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Abstract

Urbanization contributes to the loss of the world's biodiversity and the homogenization of its biota. However, comparative studies of urban biodiversity leading to robust generalities of the status and drivers of biodiversity in cities at the global scale are lacking. Here, we compiled the largest global dataset to date of two diverse taxa in cities: birds (54 cities) and plants (110 cities). We found that the majority of urban bird and plant species are native in the world's cities. Few plants and birds are cosmopolitan, the most common being Columba livia and Poa annua. The density of bird and plant species (the number of species per km(2)) has declined substantially: only 8% of native bird and 25% of native plant species are currently present compared with estimates of non-urban density of species. The current density of species in cities and the loss in density of species was best explained by anthropogenic features (landcover, city age) rather than by non-anthropogenic factors (geography, climate, topography). As urbanization continues to expand, efforts directed towards the conservation of intact vegetation within urban landscapes could support higher concentrations of both bird and plant species. Despite declines in the density of species, cities still retain endemic native species, thus providing opportunities for regional and global biodiversity conservation, restoration and education.
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... Urbanization is one of the major threats to biodiversity worldwide (Maxwell et al., 2016). The rapid sprawl and densification of urban centers has negative effects on local biotas through the novel ecological and evolutionary pressures imposed by the combination of multiple environmental factors such as habitat loss, pollution, climate change, and expansion of invasive species (Johnson and Munshi-South, 2017), which can act as ecological filters of biotic communities (Aronson et al., 2014;Spotswood et al., 2021). Yet urban scenarios span a wide range of environmental heterogeneity and greenspaces which can provide valuable refuges for native biodiversity, even rare and threatened species (Spotswood et al., 2021). ...
... First, we contrasted the structure of hummingbird-plant networks across different urban greenspaces (natural protected areas, urban parks, urban gardens, and street trees areas), and then quantified plant species importance to network structure according to plant origin, life form, and pollination syndrome. Based on previous findings highlighting the impoverishment of nectar-feeding bird assemblages in urban areas as well as the dominance of alien plant species (Aronson et al., 2014;Pauw and Louw, 2012;Puga-Caballero et al., 2020), we expected to find a high generalization of hummingbird-plant networks in urban greenspaces with less vegetation cover. Moreover, due to the behavioral flexibility of hummingbirds in urban settings (Greig et al., 2017) and the inclusion of exotic plant species as feeding resources Maruyama et al., 2019;Mendonça and Anjos, 2005) we expected that alien plant species would have an important role for network structuring across urban green areas. ...
... Citizen science platforms allowed us to compilate a robust dataset of hummingbird sightings at wide temporal and spatial scales, which is very difficult to obtain by direct and indirect observations in the field. On the other hand, different studies have shown a positive relationship between species richness with city size (i.e., larger cities have greater species pools) and landscape heterogeneity (Aronson et al., 2014;Callaghan et al., 2021;MacGregor-Fors et al., 2011), factors that Hernández, 2016), including a network of multiple urban greenspaces across the city, which represent a substantial offer of floral resources available throughout the year to hummingbirds and other pollinators . In addition, many citizens use artificial nectar feeders to attract hummingbirds to their homes, adding a bonanza complementary to floral resources that would increase the abundance and richness of hummingbirds in the city (Arizmendi et al., 2007;Maruyama et al., 2019;Meehan et al., 2020). ...
Article
The rapid sprawl of urban settings often comprises a drastic landscape transformation due to the replacement of natural vegetation by impervious surfaces. However, cities can serve as critical refuges for some native fauna, particularly for pollinators. Here we used citizen data to contrast the structure of hummingbird-plant meta-networks across different greenspaces (natural protected areas, urban parks, urban gardens and street trees areas) in a tropical megacity. We compiled hummingbird-plant visitation records in Mexico City available in two citizen science resources: iNaturalist and eBird. We first determined whether the retrieved dataset was representative to estimate network metrics by calculating sample coverage and estimating species richness in different greenspaces. Then, we characterized network structure and plant importance for network organization according to plant origin, life form and pollination syndrome. We recorded 17 hummingbirds visiting 84 plant species, encompassing a total of 742 interactions. Natural protected areas and urban parks showed a higher richness of hummingbirds and plants. All networks had low levels of connectance, specialization, and nestedness. Modularity was significant across all networks with higher values in natural protected areas and urban gardens. Native and introduced plant species showed a similar contribution to network organization. Non-ornithophilous plants were most important in natural protected areas, while tree species were most important in street trees greenspaces. Our results provide evidence of generalization of hummingbird-plant networks in urban areas. Introduced species and non-ornithophilous plants were equally important for hummingbirds, suggesting an integration of alien plants with no specialized bird pollination traits into ecological networks in urban scenarios. Promoting conservation initiatives as pollinator gardens with key native species for hummingbirds across the city could contribute to the functional connectivity and restoration of ecological interactions in cities.
... These urban-associated species responded positively to cities in other studies as well: House Sparrow (Passer domesticus), Rock Pigeon (Columba livia) and Collared Dove (Streptopelia decaocto) (Conole and Kirkpatrick 2011;Evans et al. 2009;Husté and Boulinier 2011). Aronson et al. (2014) found House Sparrow and Rock Pigeon to be cosmopolitan and appearing in more than 80% of their investigated cities globally. The observed effects of feeding guild are somewhat in concordance with the results of Evans et al. (2011), who found birds with plant-based diets to have higher densities in urban-relative to rural areas, and Pinho et al. (2016), who found granivorous species to be associated with urban areas. ...
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Land-use and land-cover change strongly affect biodiversity patterns and are assumed to be growing threats in the future. Particularly increasing urbanisation may affect species turnover and functional composition of biological communities. This study aimed to assess the characteristics of land-cover change in a medium-sized urban municipality from 2011 to 2018, and the effects of urbanisation on avian species- and functional diversity. The study was performed in Trondheim (Norway), using local land-cover maps and GBIF bird species occurrence records. GLMMs were used to model species turnover as a function of urbanisation, and the probability of species appearance and disappearance based on urbanisation and species traits. The extent of bird species turnover within a municipality-wide 500 × 500m² grid was not predicted by a changes in developed area, but the probability of disappearance and appearance of bird species varied with urbanisation and bird functional traits. Species associated with urban- or open areas showed a decreasing probability of disappearing and an increasing probability of appearing with increasing amount of developed area within grid cells. Similarly, granivorous species showed a decreasing probability of disappearing. Species feeding above ground-level showed positive responses to changes in land-cover. The probability of both appearance and disappearance, thus species turnover, increased with increasing longevity. Most functional groups respond negatively to increasing urbanisation, indicating a potential impoverishment of local avifauna with future land-cover modifications. Considering planned future land-cover changes within the municipality, the local avian communities are in danger of homogenisation. The recommendations for local management are to minimise conversion of vulnerable habitats, such as wetlands and woodlands, in particular if these are converted to developed area.
... This generally comes at the expense of the natural environment and its fauna and flora (Sol et al. 2014;Ibáñez-Álamo et al. 2017;da Silva and Gouveia 2020). Numerous studies have indicated that anthropogenic land-use changes, especially urbanisation, are a significant threat to biodiversity, particularly in the northern hemisphere (Cohen 2006;Aronson et al. 2014;Seress and Liker 2015;Ibáñez-Álamo et al. 2017;Litteral and Shochat 2017;Hersperger et al. 2018;Albert et al. 2020). However, other studies show that some of these altered landscapes generally have a mix of anthropogenic and natural elements creating mosaic urban landscapes that offer opportunities for the persistence of certain species (McCleery et al. 2012;Fournier et al. 2020;Spotswood et al. 2021;Downs et al. 2021). ...
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Urbanisation has increasingly encroached on numerous bird species' natural habitats, generally negatively affecting their persistence. Furthermore, increased human-wildlife interactions may benefit or be detrimental to the long term persistence of these species. The Spotted Thick-knee (Burhinus capensis), a ground-nesting species, persists in some mosaic urban landscapes in South Africa. We, therefore, assessed the presence of Spotted Thick-knees and their interactions with humans in the fragmented natural and human-modified landscape of Pietermaritzburg, KwaZulu-Natal. We conducted presence-only surveys at 52 locations between July 2019 and December 2020. 'Presence' locations for Spotted Thick-knee were identified via active surveying and public participation. Newspaper articles were distributed in June 2019, requesting information on Spotted Thick-knee sightings. Questionnaires were also sent to respondents to collect qualitative information regarding their perceptions and observations of this species in Pietermaritzburg. We established that the presence of Spotted Thick-knee's at known locations was not random. They were present at 30 out of 52 sites for 75% of this study's duration. Fewer sites had Spotted Thick-knees present during non-breeding months than breeding months. Respondents' feedback highlighted the pressures associated with Spotted Thick-knees persistence in human-modified mosaic landscapes, particularly predation and disturbance by domestic pets. Our study highlights that some ground-nesting birds, such as Spotted Thick-knees, persist in mosaic urban landscapes, despite the anthropogenic pressures. This study highlights the need to address the paucity of studies on ground-nesting birds in mosaic urban landscapes to determine general trends. Supplementary information: The online version contains supplementary material available at 10.1007/s11252-022-01254-3.
... Planting non-native species highly contribute to more diverse woody vegetation communities in urban areasalmost half of the non-native woody species in urban ecosystems are deliberately planted (Aronson et al., 2014;Kowarik, 2011). Around 40% of plant species in European cities are non-native (Pyšek, 1998), although lower (30%; Salinitro et al., 2018) and higher (66%; Säumel et al., 2010) proportions have also been reported (Kowarik et al., 2013;Tsiotsiou and Christodoulakis, 2010). ...
... Expansion of urban area is one of the driving forces responsible for massive changes of ecological condition (Bolund and Hunhammar 1999;Chen and Chen 2007;Li et al. 2012;Aronson et al. 2014) and loss of natural capitals (He et al. 2016). Population explosion and related infrastructure development are very common phenomena in urban area, which changes the LULC pattern (Das et al. 2020;Gao et al. 2017). ...
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Urbanization has profound influence on the changes of land use and land cover, which on the other hand exert significant impact on ecosystem services and their values, especially in the urban agglomerations. Kolkata urban agglomeration of India has been selected to determine the causes in changes of ecosystem services under present and projected land use land cover scenario. Land use land cover maps of 1990, 2000, 2010 and 2020 were prepared by support vector machine method, using LANDSAT satellite imageries and projected up-to 2040 using CA-Markov model. Built-up land was increased by 65.39% during 1990-2020 and will further increase to 76.88% by 2040. Built-up lands are mainly encroaching crop lands and wetlands. During the period of fifty years (1990-2040), the ecosystem service value will decrease from $38,486.49 to $28,060.79, with annual rate of decrement of 0.54%. During the same period, the spatial extent of very low ecosystem service value will be increased from 16.60 to 58.88%; whereas, the area coverage of very high ecosystem service value will be decreased from 2.69 to 2.35%. Water supply contributed highest ecosystem service value followed by disturbance regulation and nutrient cycling; whereas, lacking in soil formation, pollination and biological control services contributed lowest. The study will help in decision making process for sustainable management of natural resources and also provide useful guideline for the quality improvement in urban ecosystems. Keywords CA-Markov model · Ecosystem service value (ESV) · Land use/land cover (LULC) · Scenario analysis for ESV · Urban expansion
... Expansion of urban area is one of the driving forces responsible for massive changes of ecological condition (Bolund and Hunhammar 1999;Chen and Chen 2007;Li et al. 2012;Aronson et al. 2014) and loss of natural capitals (He et al. 2016). Population explosion and related infrastructure development are very common phenomena in urban area, which changes the LULC pattern (Das et al. 2020;Gao et al. 2017). ...
Article
Full-text available
Urbanization has profound infuence on the changes of land use and land cover, which on the other hand exert signifcant impact on ecosystem services and their values, especially in the urban agglomerations. Kolkata urban agglomeration of India has been selected to determine the causes in changes of ecosystem services under present and projected land use land cover scenario. Land use land cover maps of 1990, 2000, 2010 and 2020 were prepared by support vector machine method, using LANDSAT satellite imageries and projected up-to 2040 using CA–Markov model. Built-up land was increased by 65.39% during 1990–2020 and will further increase to 76.88% by 2040. Built-up lands are mainly encroaching crop lands and wetlands. During the period of ffty years (1990–2040), the ecosystem service value will decrease from $38,486.49 to $28,060.79, with annual rate of decrement of 0.54%. During the same period, the spatial extent of very low ecosystem service value will be increased from 16.60 to 58.88%; whereas, the area coverage of very high ecosystem service value will be decreased from 2.69 to 2.35%. Water supply contributed highest ecosystem service value followed by disturbance regulation and nutrient cycling; whereas, lacking in soil formation, pollination and biological control services contributed lowest. The study will help in decision making process for sustainable management of natural resources and also provide useful guideline for the quality improvement in urban ecosystems.
Article
Urbanization exposes species to novel ecological conditions. Some species thrive in urban areas, whereas many others are excluded from these human‐made environments. Previous analyses suggest that the ability to cope with rapid environmental change is associated with long‐term patterns of diversification, but whether the suite of traits associated with the ability to colonize urban environments is linked to this process remains poorly understood. World. Current. Passerine birds. We applied macroevolutionary models to a large dataset of passerine birds to compare the evolutionary history of urban‐tolerant species with that of urban‐avoidant species. Specifically, we examined models of state‐dependent speciation and extinction to assess the macroevolution of urban tolerance as a binary trait, in addition to models of quantitative trait‐dependent diversification based on relative urban abundance. We also ran simulation‐based model assessments to explore potential sources of bias. We provide evidence that historically, species with traits promoting urban colonization have undergone faster diversification than urban‐avoidant species, indicating that urbanization favours clades with a historical tendency towards rapid speciation or reduced extinction. In addition, we find that past transitions towards states that currently impede urban colonization by passerines have been more frequent than in the opposite direction. Furthermore, we find a portion of urban‐avoidant passerines to be recent and to undergo fast diversification. All highly supported models give this result consistently. Urbanization is mainly associated with the loss of lineages that are inherently more vulnerable to extinction over deep time, whereas cities tend to be colonized by less vulnerable lineages, for which urbanization might be neutral or positive in terms of longer‐term diversification. Urban avoidance is associated with high rates of recent diversification for some clades occurring in regions with relatively intact natural ecosystems and low current levels of urbanization.
Article
Greenspace or green cover is one of the major factors affecting urban avian diversity. In China, small farmlands producing vegetables are relatively common in cities. Although these farmlands could be a part of greenspaces, their habitat value for birds is rarely known. I investigated how these farmlands influenced winter bird community in two cities of southern China, using the multivariate latent variable model. I considered three green cover types: crop (mostly vegetables), weed (pioneer spontaneous vegetation), and wood (tree/shrub). I calculated the percentage of each green cover at local (50 m radius circular area) and landscape (500 m radius circular area) scales. Of 30 bird species, the abundance of 13 species decreased as crop cover decreased with increasing woody cover at the local scale, whereas the abundance of only two bird species increased with decreasing crop cover. Habitat preference of species mediated these responses, leading to a strong association between the open habit trait and the negative responses. Open habitat bird species richness was also negatively affected by decreasing local crop cover. Tree/shrub bird species richness showed a positive response to decreasing crop cover but the explanatory power of the local scale model was low. Variables at the landscape scale were rarely associated with species abundance or richness. These results suggest that small vegetable‐dominant farmlands can serve as open habitat for birds in urban areas where greenspace largely consists of tree/shrub vegetation. The results also indicate that urban bird diversity is more influenced by local habitat features than landscape‐scale features. Greenspaces are important urban infrastructure to conserve bird diversity in a city. This study shows that small vegetable‐dominant urban farmlands can serve as open habitat for birds: the positive association of open habitat species with crop vegetation cover, especially at local scale. In addition, it indicates the importance of considering species traits in the study of urban biodiversity and suggests that not all greenspaces had similar habitat values for birds.
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Information on how urban areas affect bird communities during winter in the boreal region is still scarce. With the aim of assessing such role of the urban habitats on over-wintering boreal birds, I focused on a city-wide approach in the city of Lahti (southern Finland) and two nearby forests (as controls). Point count surveys were conducted in 157 sites within the city and 30 in the control forests. In order to achieve comparable sets of data to contrast with the reference forests, I randomly selected five 30 point count sub-samples from the Lahti city-wide survey. Species richness was, in general, higher in the sub-samples from the city of Lahti. Such pattern did not show relationship with the built cover of the studied sites. Bird abundances were 3.3–5.9 times higher in the urban sub-samples when contrasted with the forest ones. Although results of this study are limited to a single city and consider one wintering season, they clearly illustrate the important role of urban systems as habitat for wintering birds in boreal systems.
Intensified urbanization has caused a linear decline in the quality of urban biodiversity and indirectly harms our current human settlement environment. Urban mountain parks provide a refuge for the animals and plants and play a vital role in satisfying residents’ lives. At present, few studies are focusing on the impact of biodiversity on human mental health benefits of urban mountain parks in high-density construction areas along the coast of the Eastern Hemisphere. Here, we examined the relationship between bird abundance, Shannon diversity, Simpson diversity, and Richness and momentary mental health (positive, negative, and anxiety) in urban mountain parks. The timed species counts method was used to conduct three surveys of birds in urban mountain parks, and linear regression was performed on the relationship between bird diversity and mental health among sites. According to the regression model results, we found no significant correlation in any disturbance levels. As urban mountain parks are an essential part of the human settlement environment, how to improve the biodiversity and mental health of urban mountain parks is one of the focuses of research on biodiversity well-being in the future. Urban planning authorities and public mental health researchers should pay attention to the importance of biodiversity in urban development and consider how to realize the beautiful vision of the harmonious coexistence of humans, animals, plants, and the environment in which we live.
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We compared the avifauna in two cities, Quebec (Canada) and Rennes (France), in order to define general responses of wildlife in an urban ecosystem. These cities have a similar urban structure that permits investigation along an urbanization gradient from downtown to rural residential areas. However, they are in opposite temperate climate and imbedded in a forested and an agricultural landscape, respectively. Plots ranging from 10 to 20 ha were surveyed in winter and spring by recording all birds seen or heard. Most plots could be located along a gradient according to proportions of vegetated open space. Both the Shannon-Wiener and Simpson indices of diversity indicated a pattern of increasing diversity from most to least urbanized areas in spring. Winter species diversity and richness was low in Quebec compared to Rennes, reflecting the much harsher winter conditions in Quebec. Breeding densities of House Sparrows (Passer domesticus) and European Starlings (Sturnus vulgaris) were quite similar in Quebec and Rennes, as were densities of European Blackbirds (Turdus merula) and its ecological equivalent in Quebec, the American Robin (Turdus migratorius). The type of surrounding landscape can not explain the Variation of species numbers within the city. If we examine the urban environment as a new ecological system rather than a degraded environment, we can regroup birds in two major species groups: the omnivorous species adapted to the urban environment and its particular food resources such as garbage and the species that find, in the urban environment, resources which they normally exploit in their usual habitat.
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1. Using data on the spatial distribution of the British avifauna, we address three basic questions about the spatial structure of assemblages: (i) Is there a relationship between species richness (alpha diversity) and spatial turnover of species (beta diversity)? (ii) Do high richness locations have fewer species in common with neighbouring areas than low richness locations?, and (iii) Are any such relationships contingent on spatial scale (resolution or quadrat area), and do they reflect the operation of a particular kind of species-area relationship (SAR)? 2. For all measures of spatial turnover, we found a negative relationship with species richness. This held across all scales, with the exception of turnover measured as β sim. 3. Higher richness areas were found to have more species in common with neighbouring areas. 4. The logarithmic SAR fitted better than the power SAR overall, and fitted significantly better in areas with low richness and high turnover. 5. Spatial patterns of both turnover and richness vary with scale. The finest scale richness pattern (10 km) and the coarse scale richness pattern (90 km) are statistically unrelated. The same is true of the turnover patterns. 6. With coarsening scale, locations of the most species-rich quadrats move north. This observed sensitivity of richness 'hotspot' location to spatial scale has implications for conservation biology, e.g. the location of a reserve selected on the basis of maximum richness may change considerably with reserve size or scale of analysis. 7. Average turnover measured using indices declined with coarsening scale, but the average number of species gained or lost between neighbouring quadrats was essentially scale invariant at 10-13 species, despite mean richness rising from 80 to 146 species (across an 81-fold area increase). We show that this kind of scale invariance is consistent with the logarithmic SAR.
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A guide to using S environments to perform statistical analyses providing both an introduction to the use of S and a course in modern statistical methods. The emphasis is on presenting practical problems and full analyses of real data sets.
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Species of Isoetes are notorious for the difficulties they present in identification. These difficulties are attributable to a series of habitat adaptations that have resulted in morphological simplicity, homoplasy, and reticulate evolution. Internal air chambers in the leaves of all taxa indicate that primitive Isoetes was aquatic. During the breakup of Gondwana, ancestors of modern taxa appear to have passed through a terrestrialization phase, which was accompanied by development of several morphological novelties and reductions including the evolution of sclerotic phyllopodia. This adaptation appears to have evolved after separation of the Indian subcontinent. A new section of the subgenus Isoetes centered in India and possessing non-sclerified, persistent leaf bases is described. Following a terrestrialization phase, several lineages became secondarily aquatic and, in some instances, once again evolved a terrestrial habitat. As a result, the genus now occupies a variety of niches, from wholly aquatic to wholly terrestrial. Most terrestrial species, found as isolated populations of basic diploids, appear to be the result of gradual speciation via isolation and genetic divergence. Some aquatic species, often found in mixed populations containing taxa of different ploides, appear to have evolved abruptly via interspecific hybridization and chromosome doubling. Evidence from distribution patterns, megaspore morphology and viability, chromosome numbers, and electrophoretic profiles of leaf enzymes supports a hypothesis of allopolyploid speciation.
The paper deals with urban ecology as a biological science and applies some of the topics of general importance in ecology to the special conditions found in towns and cities. I consider whether cities should be treated as one integrated ecosystem, or as an assemblage of various ecosystems. In contrast to the holistic, organismic concept of the ecosystem as a new hierarchical level of organization and as an evolving whole which guides the development of the species, I follow the methodological definition of Tansley (1935), who defined ecosystems as `mental isolates' for `the purpose of study'. According to Evans (1956) ecosystems can be defined at every level of the biological organization, at the level of the organisms, populations or communities. The introduction of species from other biogeographical regions is a worldwide phenomenon, but the proportion of successfully established introduced species is higher in cities than in rural or forest areas. This is due to numerous colonizing species which fit the anthropogenous habitats. Due to unequal rates of immigration and extinction of species, urban habitats show an imbalanced turnover of species. Another special feature of urban ecology is man-induced disturbance, which initiates the colonization of disturbed or newly created habitats. According to the type of substrate and the availability of diaspores there may be both primary, secondary or intermediate types of succession. Besides disturbance, the main component for structuring communities is biological interactions. In this paper I discuss some aspects of competition, predation and mutualism. The special feature of higher species' richness of cities compared with ecosystems in the countryside can be explained by the high habitat diversity of urban and industrial areas. Although some components which contribute to the complexity of communities, such as competition, are of minor importance in various urban habitats, there may be communities of high complexity. I also consider community characteristics such as stability and productivity. Since most urban communities are in a state of inequilibrium, theories of stability based on equilibrium are inadequate for urban ecosystems. The productivity of the `ecosystem city' mainly depends on the area of unsealed open space and the successional stage of the plant communities of the various habitats.
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A cladistic analysis based on rbcL sequences from a representative sample of 12 species yields a single most parsimonious tree that supports monophyly of Lycopodiaceae, Lycopodium, and Lycopodiella. Huperzia is resolved as paraphyletic to the morphologically divergent, monotypic Australasian Phylloglossum. The Huperzia-Phylloglossum clade is strongly supported and is sister group to a Lycopodium-Lycopodiella clade. These results provide the first clear evidence for the relationships of the problematic Phylloglossum drummondii. Profound differences in life cycle and morphology between Phylloglossum and other Lycopodiaceae are interpreted in terms of pedomorphosis (specifically. progenesis) and are viewed as adaptive responses to drought and brush fur. Our results show that rbcL sequence divergence among neotropical species of the supposedly ancient genus Huperzia is extremely low and that additional levels of sequence divergence indicate that most living species diversity within Lycopodiaceae ene is of relatively recent origin. Our results are consistent with a late Cretaceous or early Tertiary origin and diversification of epiphytic species within Huperzia, and three events may be linked to the diversification of angiosperms.
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Even if robust regression estimators have been around for nearly 20 years, they have not found widespread application. One obstacle is the diversity of estimator types and the necessary choices of tuning constants, combined with a lack of guidance for these decisions. While some participants of the IMA summer program have argued that these choices should always be made in view of the specific problem at hand, we propose a procedure which should fit many purposes reasonably well. A second obstacle is the lack of simple procedures for inference, or the reluctance to use the straightforward inference based on asymptotics. The procedure we propose here is essentially an MM-estimator, augmented by the estimation of its asymptotic covariance matrix to allow for approximate inference. It includes, as an extra feature, a test for a potential bias introduced by the requirement of high efficiency. The implicit and explicit choices which determine the procedure cannot be based on solid results, since finite sample studies are not yet available. The purpose of our proposal is to foster such studies as well as the collection of other experience with it.