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Trajectories from extinction: Where are missing mammals rediscovered?


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Aim To determine where mammals that are presumed to be extinct are most likely to be rediscovered, and to test predictions of two hypotheses to explain trajectories of decline in mammals. Range collapse is based on the premise that extinction rates at the edge of species ranges are highest because habitat is suboptimal, so declining species are predicted to survive longer near the centre of their ranges. We predicted that under range collapse, remnant populations are most likely be rediscovered within their former core range. Conversely, if threats usually spread across ranges, declining species will be pushed to the periphery (range eclipse), so rediscoveries are predicted at the edge of the pre-decline range. If so, species would be more likely to be rediscovered in marginal habitat, and at higher elevations than the sites from which they disappeared. Location World-wide. Methods Using data on 67 species of mammals which have been rediscovered, I tested whether species were disproportionately rediscovered in the outer 50% of their former range area or at higher elevations than their last recorded locations, and which species characteristics were associated with rediscovery location and habitat change, using both the phylogenetic generalized least squares method to account for phylogenetic non-independence and linear models of raw species data. Results Species affected by habitat loss were more likely to be rediscovered at the periphery than the centre of their former range, consistent with range eclipse caused by the spread of habitat destruction. High human population pressure predicted which species changed habitat between their previous records and rediscovery. Coastal species experienced higher human population densities, and were more likely to be rediscovered at the periphery of their former ranges, and there was some evidence of an up-slope shift associated with higher human populations at lower elevations. Main conclusion The locations of rediscoveries of species affected by habitat loss were consistent with range eclipse through a mechanism of spreading habitat loss and human population pressure, rather than with range collapse. Searches for mammals that have declined from habitat loss should include range edges and marginal habitat, especially in areas of high human population density.
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Trajectories from extinction: where are
missing mammals rediscovered?geb_624415..425
Diana O. Fisher*
The University of Queensland, School of
Biological Sciences, St Lucia 4072, Queensland,
Aim To determine where mammals that are presumed to be extinct are most likely
to be rediscovered,and to test predictions of two hypotheses to explain trajectories
of decline in mammals. Range collapse is based on the premise that extinction rates
at the edge of species ranges are highest because habitat is suboptimal, so declining
species are predicted to survive longer near the centre of their ranges. We predicted
that under range collapse, remnant populations are most likely be rediscovered
within their former core range. Conversely, if threats usually spread across ranges,
declining species will be pushed to the periphery (range eclipse), so rediscoveries
are predicted at the edge of the pre-decline range. If so, species would be more likely
to be rediscovered in marginal habitat, and at higher elevations than the sites from
which they disappeared.
Location World-wide.
Methods Using data on 67 species of mammals which have been rediscovered, I
tested whether species were disproportionately rediscovered in the outer 50% of
their former range area or at higher elevations than their last recorded locations,
and which species characteristics were associated with rediscovery location and
habitat change, using both the phylogenetic generalized least squares method to
account for phylogenetic non-independence and linear models of raw species data.
Results Species affected by habitat loss were more likely to be rediscovered at the
periphery than the centre of their former range, consistent with range eclipse
caused by the spread of habitat destruction. High human population pressure
predicted which species changed habitat between their previous records and redis-
covery. Coastal species experienced higher human population densities, and were
more likely to be rediscovered at the periphery of their former ranges, and there was
some evidence of an up-slope shift associated with higher human populations at
lower elevations.
Main conclusion The locations of rediscoveries of species affected by habitat loss
were consistent with range eclipse through a mechanism of spreading habitat loss
and human population pressure, rather than with range collapse. Searches for
mammals that have declined from habitat loss should include range edges and
marginal habitat, especially in areas of high human population density.
Biological invasion, elevation, extinction trajectory, habitat loss, mammals,
overkill, rediscovery.
*Correspondence: Diana O. Fisher, School of
Biological Sciences, Goddard Building (8), The
University of Queensland, St Lucia 4072,
Queensland, Australia.
Species presumed to be extinct are often rediscovered (MacPhee
& Flemming, 1999), and large amounts of money and effort
have been spent attempting to rediscover some high-profile
extinct vertebrates such as thylacines in Australia and ivory-
billed woodpeckers in the USA (Paddle, 2002; Wilcove, 2005).
Despite their frequently high scientific profiles and conservation
Global Ecology and Biogeography, (Global Ecol. Biogeogr.) (2011) 20, 415–425
© 2010 Blackwell Publishing Ltd DOI: 10.1111/j.1466-8238.2010.00624.x 415
importance (Diamond, 1987), until the recent study of Fisher &
Blomberg (2010), which found that mammals affected by
habitat loss with relatively large ranges are most likely to be
rediscovered, rediscoveries have been considered as idiosyn-
cratic events, so there has been no previous quantitative evalu-
ation of where species are rediscovered (Diamond, 1987;
MacPhee & Flemming, 1999).
The abundant centre hypothesis suggests that rediscoveries of
rare or declining species are most likely in the best habitat at the
core of their ranges rather than in marginal habitat at the edges,
because animal density and condition decrease at the range
periphery (Caughley et al., 1988; Sagarin & Gaines, 2002). The
abundant centre hypothesis predicts that ranges should collapse
inwards as the species declines to extinction, assuming that
peripheral populations go extinct most rapidly, leaving the last
remnants where the population was densest: a decline trajectory
of ‘range collapse’ – also termed ‘the demographic hypothesis’
(Channell & Lomolino, 2000a,b), ‘melting range’ (Rodriguez,
2002) or ‘demographic decline’ (if population densities in the
core range are relatively stable) (Hemerik et al., 2006). Support
for this idea includes studies by Nathan et al. (1996), who
showed that Israeli birds in a peripheral part of their geographic
range were more likely to go extinct, and Moritz et al. (2008),
who found evidence of inwards range collapse associated with a
decrease in habitat and climate suitability in two alpine
mammals. Hemerik et al. (2006) also argued that figures in
Channell & Lomolino (2000b) are consistent with range collapse
in about half of declining species.
There are obvious reasons to begin looking for a missing
species in the vicinity of its last recorded location; suitable
habitat might persist near the most recent site, and species at
very low densities can be virtually undetectable, although their
spatial distribution has not changed (Rout et al., 2009). On the
other hand, there are plausible reasons to expect rediscoveries to
be remote from the location of extinct populations. Recent
large-scale studies have failed to support the premise of the
abundant centre pattern of density distribution (Sagarin et al.,
2006). The range collapse hypothesis has been challenged by the
finding that severe declines at the continental scale in species
generally, and specifically in mammals and birds (Channell &
Lomolino, 2000a,b), New Zealand reptiles and frogs (Towns &
Daugherty, 1994) and a European butterfly (Thomas et al.,
2008), more often follow a trajectory outwards from the range
centre to the periphery. This decline trajectory has been termed
‘the contagion hypothesis’ (Channell & Lomolino, 2000a,b) or
‘range eclipse’ (Hemerik et al., 2006), the term used here. The
hypothesized reason for range eclipse is that anthropogenic
threats such as habitat loss and invasive predators usually spread
across species ranges in a contagion-like manner, pushing the
declining species to the edge of its former range (Towns &
Daugherty, 1994; Channell & Lomolino, 2000a; Fisher et al.,
2003). A recent global study has supported the premise of con-
tagion in the spatial distribution of habitat clearing (Boakes
et al., 2010). Rediscoveries might therefore be expected to occur
closer to the range periphery than most historical records of
species occurrence. Because search effort is expected to focus on
the historical core range, missing species might be more likely to
persist undetected for longer at the range periphery, especially if
this is in areas of low human population density. Species that
can retreat to marginal habitat may also be more likely to survive
threats affecting their historical core ranges (Caughley & Gunn,
Agents of extinction spread in three dimensions, but until
recently elevation has not received as much research attention as
two-dimensional decline trajectories in mammals. Recent
up-slope range shifts in species distributions have been exten-
sively studied in the context of climate change (Moritz et al.,
2008), and even considered as a ‘fingerprint of global warming’
(Raxworthy et al., 2008), but high elevations might also serve as
refuges from threats that spread from the coast (Channell &
Lomolino, 2000a). Historical and current urbanization, defores-
tation and other anthropogenic habitat changes are concen-
trated at low elevations (Ciesin, 2000). For example, Peh (2007)
found that montane areas of Southeast Asian islands contained
twice the proportion of undisturbed forest as lowlands, and Hall
et al. (2009) found that ten times the proportion of tropical
forest had been lost from low elevations as from montane areas
in a high-biodiversity region of Tanzania. Therefore we might
expect to often find missing species at higher elevations than the
sites from which they disappeared, even if they pre-date the era
of recent climate warming.
The aim of this study is to determine where rediscovered
species are most often found with respect to their former ranges,
habitats and elevational ranges, in order to help target search
efforts to places where missing species are most likely to persist.
I also aim to test if the location of mammal rediscoveries is
consistent with the range eclipse or range collapse hypotheses of
species decline. I ask: (1) how far away from last sightings do
rediscoveries occur; (2) are rediscoveries likely to occur in dif-
ferent habitat from the known historical habitat type and at
higher elevations than past records of missing species; (3) how
does human population density affect the location of rediscov-
eries; and (4) are missing mammals more likely to be found in
the range centre or at the range periphery?
Data and definitions
I assembled a global database of mammal species that had been
reported globally extinct or possibly extinct but have been redis-
covered (Appendix S1 in Supporting Information), and estab-
lished the status history of species included in the 2009 IUCN
Red List (IUCN, 2009), using past and present IUCN Red Lists
and related publications, primary literature, books and the
Committee on Recently Extinct Organisms mammal database
(MacPhee & Flemming, 1999: omitted
species that have been ‘rediscovered’ through taxonomic revi-
sion, and only included mammals that are named as full species
(not subspecies) and are currently considered taxonomically
valid by the IUCN (species authorities are reported in the Red
List; IUCN, 2009).
D. O. Fisher
Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd416
I recorded the date and location of last sighting and rediscov-
ery for each species. To determine if the location of rediscoveries
depended on the type of threat, I recorded available data on the
cause of extinction. In 36 of the 67 species, a single threat was
reported in the published literature as the cause of decline to
apparent extinction. In the other 31 species,one of the three main
classes of threats was reported to be the most important; either
habitat loss (deforestation, agricultural clearing, fragmentation,
degradation, overgrazing), overkill (harvesting, hunting, exploi-
tation, persecution or bycatch) or invasion (invasive predators or
diseases). I therefore recorded the main or single threat and
additional threats interacting with the major extinction driver,
such as loss of vegetation cover exacerbating predation.
To test if rediscoveries were at higher or lower elevations
than last sighting locations, I assigned an elevation category to
each species (coastal =up to 50 m a.s.l., lowland =50 to 1000 m
a.s.l., highland =occurs over 1000 m a.s.l.) and an elevation
rank at last recorded locations and rediscovery sites, in 100-m
intervals, for species in which collecting site elevations or
precise locations were published. Elevation data were collated
from the published literature on species rediscoveries (Appen-
dix S1) and from species accounts in the 2009 Red List. These
were usually the same sources as the location data. Species were
classified as having the potential opportunity to change habi-
tats if they were not restricted to sea-level environments
(beach, saltmarsh, mangrove forest), mountain tops or areas
without topographical variation (inland plains or uniformly
low-elevation islands).
To find if rediscoveries are likely in habitat which differs from
the known historical habitat type, I recorded detailed descrip-
tions of habitat and vegetation type at last recorded locations
and rediscovery sites. To examine the effect of human popula-
tion density on rediscovery location, I estimated human popu-
lation density at the last sighting and rediscovery sites in 1990
(data from the closest available time to the mean rediscovery
date) using the Gridded Population of the World database
(Ciesin, 2000), imported into ArcGIS. These data have a reso-
lution of approximately 4.5 km (Ciesin, 2000).
Because the distance between last sighting and rediscovery is
likely to scale with geographic range size, which should therefore
be included as a covariate, I recorded approximate historical
range (geographical range area before recent declines, not
current area of occupancy) in km2for species with published
estimates or maps. Because the amount of information on
former ranges varied, I assigned categories of range rank,
defined as the historical range with a precision of one order of
magnitude (1 =up to 1 km2,8=1,000,000 to 10,000,000 km2). I
also recorded the potentially important covariates of island
status, i.e. restricted to islands or not (only one species, the
dibbler, is known to occur on a continental coast as well as on
islands), and body mass (g).
I also recorded search effort (number of reported search expe-
ditions targeted to the species after it was reported extinct, and
before it was rediscovered).These reported searches are likely to
be underestimates, but I assumed that reports are proportional
to the true number of searches, because expert authors of the
IUCN Red List are required to document search effort in
their accounts of extinct and possibly extinct species, and
publications that report rediscoveries invariably discussed
the frequency of previous sightings and unsuccessful search
Spatial data
In order to test how far away from last sightings rediscoveries do
occur,and whether missing mammals more likely to be found in
the range centre or at the range periphery, I calculated the dis-
tance between last recorded locations and rediscovery sites using
the SoDA package in R (Chambers,2008), which uses the method
of Vincenty (1975) to calculate geodetic distances in metres from
map coordinates, then converted these to kilometres (R Devel-
opment Core Team, 2009). Spatial data files accompany species
range maps published by the IUCN (IUCN, 2009). However,
many were not suitable for plotting historical ranges, because
most species accounts lacked data in the field describing the range
area from which the species has been extirpated. Some maps (e.g.
the black-footed ferret, Mustela nigripes) did show detailed pre-
decline distributions, but some (e.g. most Australian species)
showed current area of occupancy. Therefore I used additional
published sources of pre-decline (historical) range maps for
rediscovered species (Oliver & Roy, 1993; Jiménez, 1996; Carr &
Robinson, 1997; Nadler et al., 2002; Monda et al., 2007 Van Dyck
& Strahan, 2008). For the 53 species with adequate data, I digi-
tized the Lambert’s azimuthal equal area projection range maps
published by the IUCN (IUCN, 2009), and overlaid historical
range boundaries onto each map, plotted with respect to coast-
lines, and coordinates of towns and landmarks such as national
parks, located using Google Earth®. I then mapped the locations
of last sighting and rediscovery sites with respect to these histori-
cal range boundaries. In order to test if species were more likely to
be rediscovered nearer the historical range periphery or range
centre, I plotted a polygon inside the former range area by
connecting points at the same distance from the range periphery
as the rediscovery site. I used this to calculate the proportional
area of each range (in pixels) that was closer to the range periph-
ery than the rediscovery site, so that species at the periphery were
scored zero (no part of the range closer to the periphery) and
species at the range centre were scored 1 (all of the rest of the
range closer to the periphery).
Statistical analysis
To test if rediscoveries were at higher or lower elevations than last
sighting locations, I used linear mixed-effects models with
species as a random factor, elevation as the dependent variable
and location (last sighting or rediscovery location) as the inde-
pendent variable. I used the same approach to model differencein
human population density between the two locations (with
species as a random factor and (log) human population density as
the dependent variable). To incorporate the two observations of
each species as a random factor, I treated the species phylo-
geny as a pedigree, using the lmekin function in the kinship
Spatial bias in mammal rediscovery
Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd 417
package in R to fit the variance–covariance matrix and estimate
fixed factor effects and the proportion of variance explained by
phylogenetic effects among species (Atkinson & Therneau,
2008). I used chi-squared tests of the raw data (with Yates’ cor-
rection) to test if rediscovery sites occurred more often than
expected at the range periphery or range centre (defined above).
To test which variables were correlated with the distance
between last sightings and rediscoveries, and rediscovery in mar-
ginal habitat, I used both the phylogenetic generalized least
squares (GLS) method to account for phylogenetic non-
independence, and linear models of raw species data (in R, R
Development Core Team, 2009). Potential correlates were geo-
graphic range, elevation, island-dwelling, threat, body size,
human population density, number of searches and years
missing. For the least squares method, I used a composite phy-
logeny based on the recent mammal supertree (Bininda-
Emonds et al., 2007; Fisher & Blomberg, 2010), with the ape
package for R (Paradis et al., 2002). For all multiple regression,
mixed-effects models, and GLS models,I selected the best model
using the minimum Akaike information criterion (AIC). For
tests in which there was no difference between phylogenetic GLS
and linear models of raw species data (GLM), I report only the
phylogenetic GLS results.
How far away from last sightings do
rediscoveries occur?
I identified 67 species of mammals that have been rediscovered
after they were presumed or feared to be extinct (Appendix S1).
A third of rediscovered species were found within 50 km of their
last known location, the median distance was 128 km and the
arithmetic mean distance was 294 53 km (SE) (Fig. 1). The
geometric mean was 86 km. Three species were found again at
their original locations (Bulmer’s fruit bat, Aproteles bulmerae,
in Papua New Guinea; Juan Fernández fur seal, Arctocephalus
philippii), in Chile; the Vanikoro flying fox, Pteropus tubercula-
tus, in the Solomon Islands). The Australian heath mouse,
Pseudomys shortridgei, was found furthest from its last recorded
location (2200 km away).
Rediscovery distance was significantly positively correlated
with species range size and elevation category [(log) range, t=
4.0, d.f. =59, P<0.001; elevation, t=2.5, d.f. =59, P=0.017], but
not independently with time missing or any of the other vari-
ables modelled (number of years missing, number of searches,
threat, body mass, island-dwelling, or human population
density). Coastal species were found closer to their original site
than lowland and highland species (coastal, 79 46 km (SE);
lowland, 362 72; highland, 256 117).
This was consistent with the restricted distributions of most
rediscovered coastal species. The range sizes of lowland and
highland species did not differ, but on average, coastal species
had ranges that were half the size of the ranges of lowland and
highland species (F2, 60 =7.8, P<0.001; coastal, rank 3.63 0.54
(SE); lowland, 5.07 0.17; highland, 4.82 0.42). There was
no difference in the reported number of searches conducted
before species were rediscovered at different elevation categories
(F2, 64 =1.8, P=0.17; coastal, 2.6 0.59 (SE); lowland, 1.7
0.26; highland, 1.4 0.29).
Are rediscoveries likely to occur in different habitat
from the known historical habitat type?
Fifteen per cent of rediscovered mammals (10 species) were
found in a different type of habitat from that of their last
Figure 1 The frequency distribution of distances between the last sighting and rediscovery locations for rediscovered species.
D. O. Fisher
Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd418
recorded locations (Table 1). All of these were tropical forest
species threatened mainly by habitat loss (eight species) or
mainly by overkill and secondarily habitat loss (two species).
The only significant covariate of this habitat change was human
population density. Species that were rediscovered in a different
habitat experienced human population densities around 11-fold
higher than species found in their original habitat (species redis-
covered in a different type of habitat from that of their historical
locations experienced a mean human population density of 455
207 people km-2, and those rediscovered in the same habitat
as expected from historical records experienced a mean human
population density of 77 16 people km-2,z=2.8, P=0.006).
Some of the species that changed habitats were rediscovered
in higher-elevation forest types than their original lowland
records, usually associated with steep limestone outcrops, and
some were found in anthropogenic vegetation (plantations of
shrub and tree crops or regrowth of native vegetation) (Table 1).
These were all areas of woody vegetation, usually near primary
forest remnants. I found no cases where rediscovered mammals
occurred in cropland, anthropogenic pasture or other
dramatically different vegetation types from the forest that they
previously occupied.
Are rediscoveries likely to occur at higher elevations
than past records?
There was an average up-slope shift of 35% between the last
recorded location and rediscovery site in species that were not
restricted to a small elevational range by specialization on
coastal or mountain-top habitats or lack of topographical varia-
tion within their ranges. In these species, the mean elevation
rank of last recorded sites was 5.2 1.2 (c. 520 m) and the
elevation of rediscovery sites was 7.0 1.2 (c. 700 m). However,
the mixed effects model testing for a difference in elevation
between locations was the only one to differ between the GLM
(raw data) and GLS (phylogenetic effects) statistical methods.
According to the GLM, this difference was strongly significant
(t=2.8, d.f. =32, P=0.008), but according to the GLS it was not
(t=1.1, d.f. =32, P=0.26).
Table 1 Mammals rediscovered in a habitat which is different from their former (pre-decline) habitat.
Species Former habitat Habitat where rediscovered
Philippine bare-backed fruit bat (Dobsonia
Lowland primary forest, including at sea level Secondary forest on karst limestone outcrops,
on steep slopes
Tonkin snub-nosed monkey (Rhinopithecus
Low-elevation and highland primary tropical
Tropical evergreen forests associated with
karst limestone hills and mountains
Eastern black-crested gibbon (Nomascus
Lower montane and limestone forests, in a
wet tropical monsoon climate, at an
altitude range of 50–900 m
Restricted to limestone forests on inaccessible
karst outcrops ranging 640–800 m in
Bougainville monkey-faced bat (Pteralopex
Mature tropical forest, including lowland
forest close to the coast of Bougainville
Now found almost entirely in primary forest
in upland areas, high-elevation mossy
Crested genet (Genetta cristata) Tropical lowland rain forest Edge of a farm where cassava and low scrub
abutted secondary forest
Malabar civet (Viverra c ivettina) Lowland forests, swamp and riparian forests
on the coastal plain. Most records were in
valleys around riparian areas
Confined to thickets (understorey of shrubs
and grasses) in cashew plantations and
highly degraded lowland forests
Rio de Janeiro arboreal rat (Phaenomys
Primary rain forest Herbaceous vegetation next to forested hills
and farmland
Brazilian arboreal mouse (Rhagomys
Lowland tropical (Atlantic) forest Heavily degraded secondary growth of
semi-deciduous tropical forest, dominated
by exotic molasses grass, Melinis
Salim Ali’s fruit bat (Latidens salimalii) Tropical montane evergreen forest Coffee and cardamom plantation adjacent to
a forest reserve
Thin-spined porcupine (Chaetomys
Lowland tropical (Atlantic) forest Extensive areas of forest cover, including
restinga (low-canopy coastal forest on
sand, a mix of species including palms and
mangroves) and abruca forest (cocoa
plantations where a number of larger
native trees are left standing)
Sources: Santos et al. (1987), Kurup (1989), Heard & Van Rompaey (1990), Flannery (1991), Wirth (1992), Bates et al. (1994), Bonvicino et al. (2001),
Parnaby (2002), Nadler (2003), Alcala et al. (2004), Paguntalan et al. (2004), Percequillo et al. (2004), IUCN (2009).
Spatial bias in mammal rediscovery
Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd 419
How does human population density affect the
location of rediscoveries?
Human population density did not differ between the last
recorded location and rediscovery site for individual species, but
sites affected by invasion had sparser human populations than
sites affected by habitat loss or overkill (difference between
habitat loss and invasion, t=3.1, d.f. =56, P=0.002; difference
between invasion and overkill, t=0.38,d.f. =56, P=0.70; densit y
at sites where species were affected by invasion 28.5 15.5 per
km2, habitat loss 170.7 69.3, and overkill 104.1 35.4).
Human population density also differed significantly between
high and coastal elevation sites (t=-2.3, d.f. =56, P=0.02;
coastal, 280 227 per km2(SE); lowland, 114 29; highland,
27 7).
Are missing mammals more likely to be found in the
range centre or at the range periphery?
Sixty per cent of rediscoveries were closer to the range periphery
than the centre; this proportion was not significant. Thirty-two
species were in the outer 50% of the range area (e.g. Fig. 2a
and b) and 21 species were in the inner 50% (e.g. Fig. 2a) (chi-
squared =2.3, d.f. =1, P=0.13). However, the proportional area
of the range that was closer to the periphery than the rediscovery
site was significantly correlated with the type of threat, human
Figure 2 Estimated historical ranges (shaded) of some rediscovered mammals, showing the location of rediscovery sites (filled circles) with
respect to range boundaries. Maps are based on azimuthal equal area projection range maps (IUCN, 2009). (a) Six Australian examples. The
long-tailed dunnart (Sminthopsis longicaudata) and heath rat (Pseudomys shortridgei) were rediscovered in the most peripheral 0–25% of
the former range (25% of the former range is closer to a range edge), and the Julia Creek dunnart (Sminthopsis douglasi), desert rat
kangaroo (Caloprymnus campestris), Hastings River mouse (Pseudomys oralis) and Leadbeater’s possum (Gymnobelideus leadbeateri)were
rediscovered in the most central 0–25% of the former range (>75% of the former range is closer to a range edge). (b) Two Caribbean
species. The Cuvier’s hutia (Plagiodontia aedium) and almiqui (Solenodon cubanus) were rediscovered in the most peripheral 0–25% of the
former range (Hispaniola and Cuba, respectively).
D. O. Fisher
Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd420
population density and elevation (difference between invasion
and habitat loss, t=2.9, d.f. =49, P=0.005; difference between
overkill and habitat loss, t=2.4, d.f. =49, P=0.02; Fig. 3).
Seventy-eight per cent of coastal species were found in the
peripheral 50% of their former range, compared with 63% of
lowland species and 20% of highland species. Species rediscov-
ered at the range centre experienced twice the human popula-
tion density (33.1 2.0 per km2) of those rediscovered at the
periphery (13.5 1.4) (effect of human population density
rank, t=2.6, d.f. =53, P=0.01; effect of elevation rank, t=2.3,
Mammal rediscovery data were only consistent with the range
eclipse hypothesis in species affected by habitat loss. It would
therefore be most effective to include range edges in searches for
missing mammals that were affected by habitat loss. There was a
significant bias towards peripheral rediscovery locations in
species affected by habitat loss (71% rediscovered at a range edge
compared with 40% of species affected by overkill). Channell &
Lomolino (2000a) argued that range eclipse is a general response
to anthropogenic threats, and made no explicit predictions
about variation in decline trajectories with specific causes. They
proposed that range contraction towards the periphery occurs
when a threatening processes such as urbanization or defores-
tation moves across the species’ range, until the species persists
only at the edge of its former distribution, where the threat does
not reach. This suggests that range eclipse should predominate
in species affected by habitat loss, which is likely to reduce or
eliminate species in progressively larger parts of the range
without affecting density in the remaining habitat (Rodriguez,
2002). In contrast, based on evidence from declining birds,
Rodriguez (2002) suggested that overkill tends to reduce overall
population density without progressively removing species from
parts of the range. If so, species declining from overkill would be
expected to show range collapse. The predicted decline trajec-
tory from invasive predators and diseases is unclear. On the one
hand, biological invasions usually spread from a single entry
point (Cassey et al., 2004). On the other hand,the mechanism of
impact is similar in invasive predators and human predators
(Owens & Bennett, 2000). Both threats reduce prey survival and
density rather than range. The idea that overkill results in range
collapse was not supported by the rediscovered mammal data,
because species affected by invasion and overkill showed no
clear pattern in decline trajectories (Fig. 3).
Rediscovery attempts invariably include surveys of the most
recent known location of the species (e.g. Kabay & Start, 1976;
Kenyon, 1977; Woods et al., 1985; Pritchard, 1989; Páez &
García, 2003; Turvey et al., 2007), but fewer than 5% of redis-
covered mammals were located at the place from which they had
disappeared. Therefore it is important not to restrict searches for
any missing mammals to the region of their last location. The
distribution of rediscovery distances had a long tail, with most
cases distant from previous records. Half of all rediscovered
species were found more than 100 km away from their last loca-
tion, including four species found more than 1000 km away
(Fig. 1). The distance at which a species can be rediscovered is
constrained by range size, so it is not surprising that range and
rediscovery distance were strongly correlated.
The idea of range eclipse has previously been tested by com-
paring the location of former and current species ranges, but the
hypothesis also predicts that declining species are eliminated
from core habitat and persist in marginal habitat that is less
favourable to their threats. A substantial minority of rediscov-
ered mammals (15%) persisted in refuges from habitat destruc-
tion, and less commonly from hunting. These species had
experienced much greater human population densities than
species that were rediscovered in a similar habitat to that in their
original locations, suggesting that human population pressure
pushed them into marginal environments (or excluded them
from non-marginal environments). There have been no previ-
ous tests of the generality of this mechanism, but there are some
cases in other taxa. For example, the takahe, Porphyrio mantelli,
seems to have been pushed into a refuge from threats, in sub-
optimal habitat. The takahe is a New Zealand bird which disap-
peared from its former stronghold of riparian lowland forest,
and was rediscovered in alpine tussock grassland, where it avoids
high densities of introduced predators but does not thrive
(Bunin & Jamieson, 1995). Further evidence of this mechanism
comes from the recent rediscovery of the Australian armoured
mist frog, Litoria lorica. This frog was ‘known to be a rain forest
specialist endemic to the Wet Tropics Bioregion’, presumed
extinct due to the invasive chytrid fungus disease (IUCN, 2009),
but it was rediscovered in 2008 in dry eucalypt forest, which
appears to be suboptimal habitat but is a less favourable envi-
ronment for the disease (C. Hoskin, pers. comm.).
Figure 3 Location of rediscovery sites (peripheral, outer 50% of
range area, or central, inner 50% of range area) with respect to
the main cause of decline in rediscovered species.
Spatial bias in mammal rediscovery
Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd 421
Mammal species with rediscovered remnant populations sur-
viving only in marginal habitat are all tropical forest mammals
threatened mainly by habitat loss, disproportionately in areas of
very high human population density. These species survived
only in rockier and steeper habitat than most of the historical
range, which would be less favourable for agricultural clearing
and forestry (e.g. the Bougainville monkey-faced bat, formerly
found in tropical lowland rain forest in Papua New Guinea and
the Solomon Islands, and now restricted to high-elevation moss
forest), or in disturbed forest and plantations (e.g. the malabar
civet, formerly found in the now non-existent habitat of coastal
riparian forest valleys in the Western Ghats region of India, and
briefly rediscovered in the dense understorey of a cashew plan-
tation; Table 1).
I propose that the range eclipse idea can also be extended to
three dimensions. Tropical deforestation and urbanization are
strongly biased towards low elevations (Ciesin, 2000; Peh, 2007;
Hall et al., 2009). Declining species should therefore be elimi-
nated from low-elevation habitat first, and rediscovery sites are
predicted to be at higher mean elevations than historical distri-
butions. As predicted,there was an average up-slope shift of 35%
between the last recorded location and rediscovery site in species
with the potential to change their elevational distribution, but
the evidence that rediscovery sites were more likely to be at
higher elevations than historical distributions was equivocal,
because the phylogenetic comparison was not significant. The
reason for disagreement between the two statistical methods is
most likely to be that phylogenetic comparative analysis is gen-
erally more conservative, because the method compares lineages
rather than tree tips (species) (Fisher et al., 2003). Additionally,
the six murid rodents and three soricid shrews in the data set
were all at low elevations, although taxonomic clustering within
elevations did not occur in the other groups with several species,
such as pteropodid bats.
Other analyses of elevational range shift in response to habitat
change have focused on North American mammals. My finding
of an up-slope shift is consistent with the descriptive analysis of
Laliberte & Ripple (2004), who found that many species such as
cougar, elk and Dall’s sheep have disproportionately lost the
portions of their historic ranges that were at low elevations.
Beever et al. (2003) found that over a large area pikas were more
likely to have been extirpated from lower-elevation sites, which
were more disturbed by roads and contained less habitat.At the
local scale, Moritz et al. (2008) stated that vegetation change at
low sites, but not at high elevations, was a likely factor in many
up-slope shifts of small mammals in Yosemite National Park,
but Larrucea & Brussard (2008) concluded that habitat change
at higher elevations moved the elevational distribution of
pygmy rabbits downwards.
Consistent with the idea that the threat from human popula-
tion pressure pushes declining species into marginal parts of
their range at low elevations, human population density at last
sighting and rediscovery sites was 10 times greater in coastal
rediscovered mammals than in species at high elevations
(>1000 m a.s.l.) and four times higher than species at low eleva-
tions (51 to 1000 m a.s.l.). Species that persisted only at the
periphery of their former ranges were more likely to be coastal.
Coastal species were missing for longer before they were redis-
covered, despite being found after more searches within smaller
areas than species at higher elevations, implying that their
remnant peripheral populations had often declined to near-
undetectable densities. This suggests that missing mammals are
not more likely to be eventually found at range edges simply
because search effort has been most intense at the centre. Pub-
lished accounts of several rediscovered coastal species also
suggest that they occurred at extremely low densities during the
time that they were missing. For example, 21 individuals of the
San Jose Kangaroo rat, Dipodomys insularis, were captured in
2005 after 15 years of unsuccessful targeted trapping on the
same small Mexican island (Espinosa-Gayosso & Álvarez-
Castaneda, 2006). The coastal Brazilian rodent Phyllomys uni-
color had not been recorded since 1824, when a single individual
was trapped in 2004. It had been the target of intensive unsuc-
cessful searches around the area where it was rediscovered in
2001, 2002, 2003, 2004 and 2005, and has not been captured
again since 2004 (Leite et al., 2007; IUCN, 2009).
The location of rediscoveries of mammals affected by habitat
loss was consistent with Channell and Lomolino’s (2000a)
hypothesis of contagion, or range eclipse, through a mechanism
of spreading habitat loss and human population pressure. The
pattern of decline suggests that these threats spread, and declin-
ing mammal distributions contracted, both outward towards
range peripheries and upward from coastal elevations, between
the times of previous location records and rediscovery. These
results imply that especially intense, repeated search effort is
needed to locate coastal mammals that have declined to near
extinction, and that these efforts are more likely to be successful
near the range periphery in coastal species. Searches for species
apparently exterminated by habitat loss and urbanization
should include peripheral areas of the probable former range,
upland rocky sites and moderately disturbed habitat. It is likely
that more tropical forest mammals currently feared extinct in
areas of high human population density survive in secondary
forest remnants; we need to find and protect these sites.
I thank Kate Jones, Jaime Jiminez, David and Meredith Happold,
Andrew Cockburn, Hideki Endo, Rainer Hutterer, Carla
Kishinami, Stefan Klose, Friederike Spitzenberger, Craig Hilton-
Taylor and Richard Fuller for providing or helping us to locate
species data. I thank Richard Fuller for advice and help with
population density mapping in ArcGIS, and Simon Blomberg
for comments, and statistical advice and help, particularly with
methods of constructing mixed effects models to incorporate
phylogenetic effects in R. This work was supported by funding
from the Australian Research Council (ARF DP0773920).
D. O. Fisher
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Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd424
Additional Supporting Information may be found in the online
version of this article:
Appendix S1 Mammals that have been rediscovered after
having been considered extinct, or possibly extinct.
As a service to our authors and readers, this journal provides
supporting information supplied by the authors. Such materials
are peer-reviewed and may be reorganized for online delivery,
but are not copy-edited or typeset. Technical support issues
arising from supporting information (other than missing files)
should be addressed to the authors.
Diana Fisher is an ecologist at the University of
Queensland. Her current research focuses on causes of
modern extinction and predisposition to extinctions
and declines in mammals and other vertebrates,
detectability of extinction, and the conservation ecology
of Australian mammals. She also works on the
evolutionary ecology of marsupial mating systems,
maternal care and life-history strategies.
Editor: Brian McGill
Spatial bias in mammal rediscovery
Global Ecology and Biogeography,20, 415–425, © 2010 Blackwell Publishing Ltd 425
... For example, it could help to establish how ecological characteristics of species interact dynamically with environmental threats to cause initial population declines, a central question in ecology that has never been resolved (Beissinger, 2000;Chichorro et al., 2019). Furthermore, output from these models is likely to provide additional practical biogeographic insights for conservation planning, including providing geographically explicit guidance for establishment and connection of reserves through landscape-scale restoration (Sweeney et al., 2019), along with more accurate assessment of the conservation value of remnant, peripheral populations (Fisher, 2011;Lesica & Allendorf, 1995). Our protocol for advancing conservation biogeography also holds potential for determining where and in what numbers species should be reintroduced (Armstrong & Seddon, 2008), and how these strategies may vary across predator inhabited (e.g. ...
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Species range contractions both contribute to, and result from, biological annihilation, yet do not receive the same attention as extinctions. Range contractions can lead to marked impacts on populations but are usually characterized only by reduction in extent of range. For effective conservation, it is critical to recognize that not all range contractions are the same. We propose three distinct patterns of range contraction: shrinkage, amputation, and fragmentation. We tested the impact of these patterns on populations of a generalist species using forward-time simulations. All three patterns caused 86–88% reduction in population abundance and significantly increased average relatedness, with differing patterns in declines of nucleotide diversity relative to the contraction pattern. The fragmentation pattern resulted in the strongest effects on post-contraction genetic diversity and structure. Defining and quantifying range contraction patterns and their consequences for Earth’s biodiversity would provide useful and necessary information to combat biological annihilation.
... Our models suggest that precipitation and seasonality are among the most important predictors of L. flavicauda presence, therefore such changes could have dire consequences for the species. This is especially true as lower-altitude species migrate to occupy higher elevations with climate change, increasing competition for resources (Fisher, 2011). In the case of the two Lagothrix species considered here, this could also lead to an overlap in their distributions, further increasing competition between these and other primate species. ...
The Tropical Andes Biodiversity Hotspot holds a remarkable number of species at risk of extinction due to anthropogenic habitat loss, hunting, and climate change. One of these species, the critically endangered yellow-tailed woolly monkey (Lagothrix flavicauda), was recently observed in the region Junín, 206 km south of its previously known distribution. This range extension, combined with continued habitat loss, calls for a reevaluation of the species distribution, and available suitable habitat. Here, we present novel data from surveys at 53 sites in the regions of Junín, Cerro de Pasco, Ayacucho, and Cusco. We encountered L. flavicauda at 9 sites, all in Junín, and the congeneric Lagothrix lagotricha tschudii at 20 sites, but never in sympatry. Using these new localities along with all previous geographic localities for the species, we made predictive species distribution models based on ecological niche modeling using a generalized linear model and maximum entropy. Each model incorporated bioclimatic variables, forest cover, vegetation measurements, and elevation as predictor variables. The model evaluation showed >80% accuracy for all measures. Precipitation was the strongest predictor of species presence. Habitat suitability maps illustrate potential corridors for gene flow between the southern and northern populations, although much of this area is inhabited by L. l. tschudii whereas L. flavicauda has yet to be officially confirmed in these areas, by these or any other scientific surveys. An analysis of the current protected area (PA) network showed that ~75% of remaining suitable habitat is unprotected. With this, we suggest priority areas for new PAs or expansions to existing reserves that would conserve potential corridors between L. flavicauda populations. Further surveys and characterization of the distribution in intermediate areas, combined with studies on gene flow through these areas, are still needed to protect this species.
... Large-bodied species are also more likely to be in conflict with humans over areas suitable for rangelands or agricultural purposes and are often selectively harvested by humans (40), pushing them into poor productivity or barren lands (11). Small range size is associated with ecological marginalization as land-use change within their core "primary" habitat can leave low density, capped populations in the remaining marginal habitats (43,44). We show intrinsic (geographic range size and body mass) and extrinsic factors (geographic range loss) increase extinction risk. ...
Human land-use results in widespread range change across taxa. Anthropogenic pressures can result in species' realized niches expanding, shifting, or contracting. Marginalization occurs when contraction constrains species to the geographic or ecological extremes of their historic niche. Using 4,785 terrestrial mammal species, we show that range contraction results in niche space and habitat diversity loss. Additionally, ecological marginalization is a common consequence of range contraction caused by human land use change. Remnant populations become located in the climatic and topographic extremes of their historic niche that are more likely to be at the periphery of their historic niche at greater distances from historic niche centroids. This ecological marginalization is associated with poor performance and increased extinction risk independent of geographic range loss. Range loss and marginalization may create a "double whammy" in vulnerable groups, such as large-bodied species and species with small geographical range size. Our results reveal a hitherto unrecognized conservation threat that is vital to incorporate into conservation assessment and management.
... Climate and land-cover change are major threats to biodiversity conservation (Davison et al., 2021;Garcia et al., 2014). In response to these threats, species may shift their distribution ranges (Fisher, 2011). Such range shifts are likely to result in a spatial mismatch between current protected areas (PAs) and future species' range (Li et al., 2015;Peng et al., 2021), weakening the effectiveness of PAs (Carvalho et al., 2019). ...
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Species shift their distribution in response to climate and land-cover change, which may result in a spatial mismatch between currently protected areas (PAs) and priority conservation areas (PCAs). We examined the effects of climate and land-cover change on potential range of gibbons and sought to identify PCAs that would conserve them effectively. We collected global gibbon occurrence points and modeled (ecological niche model) their current and potential 2050s ranges under climate-change and different land-cover-change scenarios. We examined change in range and PA coverage between the current and future ranges of each gibbon species. We applied spatial conservation prioritization to identify the top 30% PCAs for each species. We then determined how much of the PCAs are conserved in each country within the global range of gibbons. On average, 31% (SD 22) of each species' current range was covered in PAs. PA coverage of the current range of 9 species was <30%. Nine species lost on average 46% (SD 29) of their potential range due to climate change. Under climate-change with an optimistic land-cover-change scenario (B1), 12 species lost 39% (SD 28) of their range. In a pessimistic land-cover-change scenario (A2), 15 species lost 36% (SD 28) of their range. Five species lost significantly more range under the A2 scenario than the B1 scenario (p = 0.01, SD 0.01), suggesting that gibbons will benefit from effective management of land cover. PA coverage of future range was <30% for 11 species. On average, 32% (SD 25) of PCAs were covered by PAs. Indonesia contained more species and PCAs and thus has the greatest responsibility for gibbon conservation. Indonesia, India, and Myanmar need to expand their PAs to fulfill their responsibility to gibbon conservation. Our results provide a baseline for global gibbon conservation, particularly for countries lacking gibbon research capacity.
... All current diversities exhibited significant positive correlations between diversity and elevation ranges, whereas this relationship was non-significant for the natural diversity of megafauna and large species diversity. Human accessibility may be highly correlated with elevation range as suggested by a strong global correlation between elevation slope and remaining tree cover and by a higher elevation in new than in old records for re-discovered presumed extinct mammals (Fisher, 2011). Steep mountains may offer a refuge from humans, both prehistorically (Johnson, 2002) and today (Gavashelishvili & Lukarevskiy, 2008). ...
Aim: To assess the extent to which humans have reshaped Earth's biodiversity, by estimating natural ranges of all late Quaternary mammalian species, and to compare diversity patterns based on these with diversity patterns based on current distributions. Location: Globally Methods: We estimated species, functional and phylogenetic diversity patterns based on natural ranges of all mammalian species (n=5747 species) as they could have been today in the complete absence of human influence through time. Following this we compared macroecological analyses of current and natural diversity patterns to assess if human-induced range changes bias for evolutionary and ecological analyses based on current diversity patterns. Results: We find that current diversity patterns have been drastically modified by humans, mostly due to global extinctions and regional to local extirpations. Current and natural diversities exhibit marked deviations virtually everywhere outside sub-Saharan Africa. These differences are strongest for terrestrial megafauna, but also important for all mammals combined. The human-induced changes led to biases in estimates of environmental diversity drivers, especially for terrestrial megafauna, but also for all mammals combined. Main conclusions: Our results show that fundamental diversity patterns have been reshaped by human-driven extinctions and extirpations, highlighting humans as a major force in the Earth system. We thereby emphasize that estimating natural distributions and diversities is important to improve our understanding of the evolutionary and ecologically drivers of diversity as well as for providing a benchmark for conservation.
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(Chinese Title: 中国东部灵长类及其他常见兽类的分布变迁:1573~1949——基于地方志与 GIS 技术的量化分析. The final version was submitted to Sun Yat-sen University Library and The Ministry of Education of the People's Republic of China on December 22, 2022.) Background: Primatology is an important branch of biological anthropology, and it is a cross-disciplinary area with biology, psychology, etc.. Humans are causing the 6th Mass Extinction since several hundred years ago. The long-term co-existence between people and wild animals exerted a long-term and formative influence on the distribution of animals. And mammals, especially primates and other large/medium-sized mammals, had a particularly close relationship with people and were affected severely, thus become important indicators of ecological change. The human population of China, especially in eastern China, increased rapidly from the late Ming Dynasty to the Republic of China (ROC), and the distribution of wild animals including primates was greatly affected. Numerous local gazetteers in Ming dynasty, Qing Dynasty and ROC are well preserved today, and their records of local products are valuable resources for researching the historical biodiversity. However, previous studies only focused on the records of present animal and ignored the records of absent animal, resulting in obvious biases, and there is still a lack of quantitative studies. In order to understand the changes of the distribution of mammals and the influence from the population increasing in China better, I made full use of the records in local gazetteers to reconstruct the distribution of mammals and analyzed the distribution history of large and medium-sized mammals quantitatively. Methods: I established the Database of Wild Mammal Records in Chinese Local Gazetteers. And innovatively, I fixed the biases in previous researches, i.e. I analyzed the historical changes of biodiversity by using the data of both presence and absence records of mammals. In eastern China from 1573 to 1949 (sorted into 4 periods), I reconstructed the distribution of 14 kinds of mammals which sorted in 5 functional groups with ecological values by using ArcGIS 10.3 software. The mammals are: (1) primates: “yuan” - gibbons & Colobinae(including langur monkeys and snub-nosed monkeys, different to modern taxonomy in Chinese) and “hou” - macaque monkeys; (2)large carnivores: tigers, leopards and bears; (3)medium-sized carnivores: wolves, foxes, “li”(civets, including Felinae and Viverridae, different to modern taxonomy in Chinese), dholes and mustelids; (4)large deer: large deer as a whole (including moose); (5)medium-sized deer: “Zhang-She”(including water deer and musk deer), muntjac deer and roe deer. I used statistical software, e.g. SPSS, Fragstats and SmartPLS, to analyze the changes of distribution(area, altitude, slope gradient and fragmentation index) and the impact from the increase of human population. And analyzed the indexes of functional group richness and species(kinds) richness combined with the relevant events of human population history, to show ecological environmental changes in each provincial-level administrative regions. Results: (1)In general in all periods, with the increase of human population, the distribution area of primates, large carnivores, large-sized deer and medium-sized deer retracted, the mean altitude and mean slope gradient increase and the distribution changed from distributed widely to be confined in mountainous areas with high altitudes and high slopes, as the “refuge effect”. (2)The distribution of medium-sized carnivores expanded in general, confirming to be a typical ecological decline phenomenon - mesopredator release. The mean altitude and mean slope gradient also increase, but meaning expand from plains to mountains. (3)The ecological environment in the research area deteriorated with the increase of human population, but some areas in some periods recovered temporarily after specific events e.g. wars in Sichuan in late Ming–early Qing, Taipingtianguo rebellion, muslin anti-Qing revolts in Tongzhi reign. Conclusion: (1)Based on the reconstruction, I provide directive evidences of the human interference on the historical distribution of mammals, and show the specifics. Thus, quantitatively, I prove that the increase of local human population played a significant role in this process. The stereotype “wild large/medium-sized mammal live in hilly areas” is not a natural status but a man-made phenomenon in long term. The results provide a support for further researches. (2)Pioneeringly, I discovered that the environment in eastern China experienced the mesopredator release phenomenon in recent centuries, providing a base for further researches by researchers. (3)And my innovative reorganization of local gazetteers and the application of quantitative methods also provide examples for similar further researches. Keywords: Primate; Local Gazetteer; Historical Zoogeography; Quantitative History; 6th Mass Extinction 背景:灵长类学是生物人类学的重要分支,也是人类学与生物学、心理学及其他学科的交叉领域。数百年来,人类正逐步造成第六次物种大灭绝。人类与野生动物长期相处,对动物分布格局产生了长期且塑造性的影响,而兽类(即哺乳纲动物)尤其是包括灵长类动物在内的大中型兽类与人类关系密切,受影响亦尤为明显,是生态变化的重要指示性物种。明后期至民国是中国,尤其是中国东部人口急速增长的时期,灵长类等大中型兽类分布受影响明显,且该时期地方志资源丰富,明代、清代及民国时期的地方志大量保存至今,其对各地物产的记载是研究历史上生态多样性的宝贵资源。但已有相关研究只关注动物在当地分布(Presence)的记录,而忽略了动物在当地不分布(Absence)的记录,造成明显偏差,且量化研究尚十分欠缺。为更清楚地了解灵长类等兽类分布变化及其受到中国人口剧增的影响,笔者充分利用地方志中的记载,重拟各类曾广泛分布的灵长类等大中型兽类分布情况并量化分析其分布变迁历史。 方法:笔者建立了中国地方志兽类记录数据库,创新性地修正已有研究的偏差,在新方法中同时使用兽类分布与不分布的数据插值制图重拟其分布的历史变迁。以1573年(万历元年)至1949年间(分四阶段)的中国东部大陆地区为时空范围,笔者使用地理信息系统软件ArcGIS 10.3重拟14类兽类动物的分布,并根据生态意义将这些兽类划分为5个生态功能群,即(1)灵长类功能群:猿类(长臂猿以及含叶猴与金丝猴在内的疣猴,与现代科学分类体系所指猿类不同)、猴类(猕猴属);(2)大型食肉兽类功能群:虎、豹类、熊类;(3)中型食肉目兽类功能群:狼、狐类、狸类(猫亚科与灵猫科,与现代科学分类体系所指狸类不同)、豺、鼬类;(4)大型鹿类功能群:大型鹿类整体(含麋);(5)中型鹿类功能群:獐麝类(獐与麝类)、麂类、狍。笔者通过SPSS、Fragstats、SmartPLS等统计软件量化分析分布的面积、海拔、坡度与破碎化程度等变化情况及分析人口剧增对动物分布的影响;并根据功能群数与大中型兽类种类数两种指标对各省区的大中型兽类多样性变化进行梳理,结合人口史资料研究当地生态变迁。 结果:(1)总体上,随着人口剧增,灵长类、大型食肉目兽类、大型鹿类及中型鹿类的分布面积均有不同程度的缩减,分布平均海拔与平均坡度均有所提升,其分布从较广泛分布缩减至主要在高海拔大坡度的山地分布,产生“避难所效应”。(2)而中型食肉目兽类的分布总体上实现了扩张,经证实为中型捕食者释放效应这一典型的生态衰退现象,其分布平均海拔与平均坡度亦有所提升,但主要为从平原地区向山地扩散。(3)量化证实研究区域的大中型兽类多样性总体上随着人口增长而恶化,但明末清初四川战乱、太平天国运动、同治年间回民反清斗争等事件后部分地区的多样性在特定阶段有所恢复。 结论:(1)基于重拟,笔者给出了历史上人类干扰灵长类等大中型兽类分布的直接证据并展示了具体变化过程,量化证实中国东部人口增长在大中型兽类分布缩减过程中起了明显的作用,“大中型兽类主要在山地分布”这一刻板印象并非自然状态,而是人类长期塑造的结果,为学界提供了进一步研究的支持。(2)笔者首次发现了近世中国东部经历了中型捕食者释放效应现象,为学界提供了进一步研究的基础。(3)同时笔者对地方志动物记载的创新性整理及量化处理,也将为将来类似研究提供范例。 关键词:灵长类,地方志,历史动物地理学,量化历史学,第六次大灭绝
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One third of missing mammal species thought to be extinct have been rediscovered. Determining extinction correctly, without misinterpreting negative evidence, is difficult and takes significant effort, especially for small, cryptic species. The Morro Bay kangaroo rat (MBKR), Dipodomys heermanni morroensis, is a small nocturnal rodent suspected of being extinct. This is because it has not been seen since 1986 despite three range-wide surveys conducted between 1995 and 2012, a recent scent-detecting dog survey, and over a dozen localized surveys. Causes of decline have been reported and the primary causes are thought to be development-driven habitat loss and ecological succession. Given this, we suspect that if the MBKR is extant, then it occurs in the periphery of its historical range. We summarize a survey of the Morro Bay sandspit, an area not previously considered part of MBKR’s range but that has the potential to be occupied. Inferences from the subspecies’ closest relative, Dipodomys heermanni arenae, were used to inform surveys and detection probability estimates for MBKR. Visual surveys of the sandspit in areas with the greatest probability of displaying signs yielded few occurrences of possible signs. Camera traps were deployed in winter and summer at locations with possible signs, but, despite occupancy model detection probabilities of 0.88 in winter and 0.97 in summer, there were no detections of MBKR. Given detection probability estimates inferred from Dipodomys heermanni arenae, the conditional occupancy estimate that MBKR are present on the sandspit but were missed by all cameras on all nights of surveying is extremely low (5 × 10−6). We conclude that the MBKR is not present on the Morro Bay sandspit, at least not in the habitat where its presence was most likely to be detected. Future surveys for this small, cryptic species will need to adapt to a combination of low expected occupancy and high expected detection probability.
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Did the end-Cretaceous mass extinction event, by eliminating non-avian dinosaurs and most of the existing fauna, trigger the evolutionary radiation of present-day mammals? Here we construct, date and analyse a species-level phylogeny of nearly all extant Mammalia to bring a new perspective to this question. Our analyses of how extant lineages accumulated through time show that net per-lineage diversification rates barely changed across the Cretaceous/Tertiary boundary. Instead, these rates spiked significantly with the origins of the currently recognized placental superorders and orders approximately 93 million years ago, before falling and remaining low until accelerating again throughout the Eocene and Oligocene epochs. Our results show that the phylogenetic 'fuses' leading to the explosion of extant placental orders are not only very much longer than suspected previously, but also challenge the hypothesis that the end-Cretaceous mass extinction event had a major, direct influence on the diversification of today's mammals. Molecular data and the fossil record can give conflicting views of the evolutionary past. For instance, empirical palaeontological evidence by itself tends to favour the 'explosive model' of diversification for extant placental mammals 1 , in which the orders with living representatives both originated and rapidly diversified soon after the Cretaceous/Tertiary (K/T) mass extinction event that eliminated non-avian dinosaurs and many other, mostly marine 2 , taxa 65.5 million years (Myr) ago 1,3,4. By contrast, molecular data consistently push most origins of the same orders back into the Late Cretaceous period 5-9 , leading to alternative scenarios in which placental line-ages persist at low diversity for some period of time after their initial origins ('phylogenetic fuses'; see ref. 10) before undergoing evolutionary explosions 1,11. Principal among these scenarios is the 'long-fuse model' 1 , which postulates an extended lag between the Cretaceous origins of the orders and the first split among their living representatives (crown groups) immediately after the K/T boundary 8. Some older molecular studies advocate a 'short-fuse model' of diversification 1 , where even the basal crown-group divergences within some of the larger placental orders occur well within the Cretaceous period 5-7. A partial molecular phylogeny emphasizing divergences among placental orders suggested that over 20 lineages with extant descendants (henceforth, 'extant lineages') survived the K/T boundary 8. However, the total number of extant lineages that pre-date the extinction event and whether or not they radiated immediately after it remain unknown. The fossil record alone does not provide direct answers to these questions. It does reveal a strong pulse of diversification in stem eutherians immediately after the K/T boundary 4,12 , but few of the known Palaeocene taxa can be placed securely within the crown groups of extant orders comprising Placentalia 4. The latter only rise to prominence in fossils known from the Early Eocene epoch onwards (,50 Myr ago) after a major faunal reorganization 4,13,14. The geographical patchiness of the record complicates interpretations of this near-absence of Palaeocene crown-group fossils 14-16 : were these clades radiating throughout the Palaeocene epoch in parts of the world where the fossil record is less well known; had they not yet originated; or did they have very long fuses, remaining at low diversity until the major turnover at the start of the Eocene epoch? The pattern of diversification rates through time, to which little attention has been paid so far, might hold the key to answering these questions. If the Cretaceous fauna inhibited mammalian diversification , as is commonly assumed 1 , and all mammalian lineages were able to radiate after their extinction, then there should be a significant increase in the net per-lineage rate of extant mammalian diversification , r (the difference between the per-lineage speciation and extinction rates), immediately after the K/T mass extinction. This hypothesis, along with the explosive, long-and short-fuse models, can be tested using densely sampled phylogenies of extant species, which contain information about the history of their diversification rates 17-20. Using modern supertree algorithms 21,22 , we construct the first virtually complete species-level phylogeny of extant mammals from over 2,500 partial estimates, and estimate divergence times (with confidence intervals) throughout it using a 66-gene alignment in conjunction with 30 cladistically robust fossil calibration points. Our analyses of the supertree indicate that the principal splits underlying the diversification of the extant lineages occurred (1) from 100-85 Myr ago with the origins of the extant orders, and (2) in or after the Early Eocene (agreeing with the upturn in their diversity known from the fossil record 4,13,14), but not immediately after the K/T boundary, where diversification rates are unchanged. Our findings-that more extant placental lineages survived the K/T boundary than previously recognized and that fewer arose immediately after it than previously suspected-extend the phylogenetic fuses of many extant orders and indicate that the end-Cretaceous mass extinction event had, at best, a minor role in driving the diversification of the present-day mam-malian lineages. A supertree with divergence times for extant mammals The supertree contains 4,510 of the 4,554 extant species recorded in ref. 23, making it 99.0% complete at the species level (Fig. 1; see also
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An analysis of the elevational distributions of Southeast Asian birds over a 28-year period provides evidence for a potential upward shift for 94 common resident species. These species might have shifted their lower, upper, or both lower and upper boundaries toward a higher elevation in response to climate warming. These upward shifts occurred regardless of habitat specificity, further implicating climate warming, in addition to habitat loss, as a potentially important factor affecting the already imperiled biotas of Southeast Asia.
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This contribution provides an analytical accounting of mammal species that have disappeared during the past 500 years—the “modern era” of this chapter. Our choice of date was dictated by several considerations, but two are paramount. ad 1500 marks more or less precisely the beginning of Europe’s expansion across the rest of the world, a portentous event in human history by any definition. It is an equally momentous date for natural history because it marks the point at which empirical knowledge of the planet began to burgeon exponentially. These two factors, linked for both good and ill for the past half-millennium, have affected every aspect of life on earth, and are thus fitting subjects to commemorate in a record such as this.
The Bahian giant tree rat Phyllomys unicolor (Wagner) was described from a single specimen collected in the early nineteenth century, and it has not been recorded since. It was included on tha Brazilian endangered species list, and considered extinct by some. Here we report the rediscovery of P. unicolor around the type locality in the Atlantic forest of southeastern Bahia, eastern Brazil. We trapped only one young individual during seven expeditions to ten localities in the area. The phylogenetic distinctiveness of this taxon based on the mitochondrial cytochrome b gene is clear, in spite of uncertainties regarding clade support. The evolutionary uniqueness of P. unicolor was confirmed by a high level of sequence divergence from congeneric species. We propose that the Bahian giant tree rat should be globally listed as Critically Endangered by the World Conservation Union. Phyllomys unicolor seems to be restricted to swamp forests and it does not occur in any protected area. Intensive field studies should be carried out in the region to locate populations and to study ecological attributes of this species. The rediscovery of P. unicolor draws attention to the biological importance and the lack of protected areas in this region of Atlantic forest.
Significant population declines are typically used to diagnose the level of threat faced by endangered species. In contrast, conservation strategies for these species often focus on setting aside parts of their ranges into protected areas, without regard for the distribution of population abundances within those ranges. Since abundances are not uniformly distributed within a species' range, different portions of the range may be of different conservation value. This article examines the relationship between the decrease in abundance of a taxon and the resulting pattern in the contraction of its geographical distribution. Three possible types of decline are considered. High-abundance-biased (HAB). declines occur when the overall decline in abundance occurs predominantly in the portions of the range where abundances are highest. Here, while the total abundance may significantly decline, the range can remain unchanged. Conversely, in low-abundance-biased (LAB) declines, the decline occurs predominantly in areas where abundances are lower, thus leading to a relatively faster decline in range than in abundance. In a range-wide decline (RW), all areas are equally likely to experience a decline, and the relative changes in both range size and total abundance depend on the initial abundance profile. Data for 27 declining bird species, obtained from the North American Breeding Bird Survey, show that the majority exhibit patterns consistent with an HAB decline during the last three decades. This suggests that efficient strategies for preventing or slowing a decline should concentrate conservation efforts in high-abundance areas. The designation of a nature reserve in a portion of the range where the species is simply "present" may coincide with an area with low probability of long-term persistence, and thus be an inefficient allocation of limited conservation resources.
(1) We suggest a theoretical framework for considering limits to relatively stable distributions and illustrate some of the points raised with information on the distribution of two species of kangaroos. (2) If an attribute such as density or condition is low at the periphery but rises progressively towards the core of the distribution, its trend is described as a `ramp'. If the level of the attribute differs little between the periphery and the core of the distribution its trend forms a `step' at the range boundary. (3) Should density form a ramp inwards from the boundary whereas the mean well-being of the animals (e.g. body condition, growth, weight, recruitment) forms a step, the factor limiting distribution is likely to be a resource that is utilized consumptively or pre-emptively. (4) Should both density and well-being form a ramp, the implicated factor is a component of climate, an unmodifiable resource, or a facultative predator, parasite or pathogen. (5) Should both density and well-being step at the range boundary, the factor controlling the position of the boundary is likely to be the substrate (e.g. a rock type). (6) Two kangaroo populations were sampled at the core and periphery of their respective ranges. The southern (=`western') grey kangaroo Macropus fuliginosus (Desmarest) exhibited a ramp of both density and well-being which, in combination with ecological information on this species, suggested that the edge of the range was positioned by a component of climate perhaps interacting with an unmodifiable resource. (7) The eastern grey kangaroo Macropus giganteus Shaw exhibited a ramp of density but a step of well-being, implicating a renewable resource as the factor determining the inland boundary of distribution. (8) Density and distribution are likely to be different aspects of the same thing except where the limiting factor or combination of factors is or includes a renewable resource consumed by the animals.