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The outstandingly speciose epiphytic flora of a single strangler fig (Ficus crassiuscula) in a Peruvian montane cloud forest
Abstract
An unprecedented total of 190 holo-epiphytic and five hemi-epiphytic vascular plant species were collected from the canopy and the trunk of a single strangler fig (Ficus crassiuscula) in a Peruvian montane cloud forest. A large majority of the vascular species were rare in occurrence, suggesting a high proportion of patchily distributed species within the cloud forest. One hundred and fourteen of the vascular epiphyte species were orchids, 37 species were ferns, and 17 species were bromeliads. Seventy-three of the orchid species belonged to the Pleurothallidinae. Perú is one of the global strongholds of remaining unmodified tropical montane cloud forest. However, cloud forest studies on any topic emanating from Peru´ are relatively rare. The outstanding epiphyte species richness of a single tree highlights both the importance of cloud forests for global biodiversity, and the urgency for more research and conservation initiatives within the cloud forests of Perú. INTRODUCTION Peruvian montane cloud forests are one of the global strongholds of remaining unmodified tropical montane cloud forest (Mulligan, this volume). However, they have received comparatively little scientific attention until now (e.g. Frahm, 1987: Leo, 1995; Weng et al. 2004; Gomez-Peralta et al., 2008) and are under increasing threat of deforestation (Young and León, 1995; Mulligan, this volume). The extinction rate of plant species through cloud forest removal in Perú is unknown because most cloud forests have not been botanically prospected (Honorio and Reynel, 2004). Epiphyte flora makes up a large component of plant diversity in Andean forests (Gentry and Dodson, 1987a; Kelly et al., 1994; Bussmann, 2001; Nieder et al., 2001, cf. Gradstein et al., this volume; Krömer and Gradstein, this volume).
... Vascular epiphytes, a diverse group of almost 30,000 species with mostly tropical distributions (Zotz 2013), are especially suitable for this approach, given high functional equivalence amongst species (Catchpole and Kirkpatrick 2011). Because theory on the mechanisms underlying community structure in vascular epiphytes has only recently started to emerge (Kitching 2006, Burns 2007, Burns and Zotz 2010, Mendieta-Leiva and Zotz 2015, Taylor et al. 2016, our current understanding of the structure of vascular epiphyte communities is mainly based on a few deterministic axes. ...
... Primary factors are vertical abiotic gradients (Griffiths and Smith 1983, Hietz and Briones 1998, Petter et al. 2016, host tree identity (Laube andZotz 2006, Wagner et al. 2015), and host tree size and age (Flores-Palacios andGarcía-Franco 2006, Taylor et al. 2016). Even taken together these factors still hardly suffice to explain the many aspects of community structure in epiphytes, such as frequently observed extreme local patchiness or very high local or point diversity (Catchpole and Kirkpatrick 2011), which are indicative of a high degree of ecological equivalence among many species. Hence, stochasticity (e.g. ...
Vascular epiphytes form a diverse group of almost 30 000 species, yet theory concerning their community structure is still largely lacking. We therefore employed the simplest models of biodiversity, (near‐)neutral models, to generate hypotheses concerning their community structure. With recently developed tools for (near‐)neutral models we analyzed species abundance data from many samples in Central and South America which we divided into four metacommunities (Mesoamerica, Central America, Amazonia and Paraná), where for each metacommunity we considered two subsets differing in dispersal syndrome: an animal‐dispersed guild and a wind‐dispersed guild. We considered three models differing in the underlying speciation mode. Across all metacommunities, we found observed patterns to be indistinguishable from patterns generated by neutral or near‐neutral processes. Furthermore, we found that subdivision in different dispersal guilds was often supported, with recruitment limitation being stronger for animal‐dispersed species than for wind‐dispersed species. This is the first time that (near‐)neutral theory has been applied to epiphyte communities. Future efforts with additional data sets and more refined models are expected to further improve our understanding of community structure in epiphytes and will have to test the generality of our findings. This article is protected by copyright. All rights reserved.
... 40%) by leaf litter, receives c. 12% of above canopy PPFD and is situated in acidic soils (pH 4.4) with high organics, low macronutrients and an average bulk density of 0.46 g/cm 3 (Taylor, 2008). The site is well known for its extraordinarily speciose epiphytic flora, with an unprecedented 195 species of vascular epiphytes (Catchpole & Kirkpatrick, 2010) and 110 species of non-vascular epiphytes (Romanski et al., 2011) each being recorded from single trees within the study area, for which the current list of vascular epiphytes recorded is at c. 225 species (unpublished data, D. Catchpole). Gómez (1999) found 154 tree species in a 1-ha study plot adjacent to that of the present study, in which 204 species (per ha) of understorey herbs were found, principally of the Piperaceae, Urticaceae, Asteraceae and Melastomataceae (Taylor, 2008). ...
... The 136 species recorded in the present study is very high for a montane forest at this altitude. Gómez (1999) found an even higher 154 tree species (in the ≥10 cm class) in an adjacent plot, in which an unprecedented 195 species of vascular epiphytes were found in a single tree (Catchpole & Kirkpatrick, 2010). Within this plot, Taylor (Taylor, 2008) also found a very high 204 species of understorey herbs, Romanski et al. (Romanski et al., 2011) found an unprecedented 110 species of non-vascular epiphytes in a single tree and c. 225 species of vascular epiphytes have been recorded on the largest trees (unpublished data, D. Catchpole). ...
The Cordillera Yanachaga is a semi-isolated Andean range protruding into
the Peruvian Amazon that houses an important area of montane cloud forests
on both windward and leeward slopes. Despite the importance of these
forests for biodiversity and the provision of ecosystem services for nearby
populations, their orographic variation in climate and forest ecology had not
been previously described. Climatic and forest parameters were studied
along an orographic gradient consisting of three sites, a windward slope
forest at 2400 masl, a ridge forest on the mountain pass at 2800 masl and a
leeward slope forest at 2400 masl. Common climatic measurements and
visibility were recorded from canopy towers within 1-ha vegetation sampling
plots, from which environmental data and taxonomic, foliage and structural
characters of all stems ≥5 cm DBH were collected.
Despite its orographic location, the leeward forest received marginally less
rainfall than the ridge forest and considerably more rainfall that the
windward forest. The temperature variation found was attributed to altitude
and an afternoon Foehn effect, while the orographic variation in PPFD was
very strongly correlated to fog frequency. The ridge and windward forests
showed higher canopy fog immersion (c. 75%) and a higher frequency of
simultaneous rain and fog events, while the leeward forest showed less fog
immersion (c. 20%) and higher rain frequency. The ridge and windward
forests were affected principally by easterly air masses, while the leeward
forest showed signs of localized phenomena originating from the Oxapampa
valley to the west. The leeward forest displayed more climatic variation and
larger parameter ranges, which were reflected in greater species richness,
basal area, canopy height, foliage area and leaf size. Floristic associations
within plots reflected sheltered and exposed regions. Forests at all the sites
had stem densities and basal areas at the lower end of those recorded in
other regions.
At the leeward site, light and moderate fog events generally displayed diurnal
temperatures and PPFD more similar to clear sky events than to rain events,
reflecting the warm clear upper atmosphere conditions under which they
form. Dense fog events tended to mimic microclimatic conditions during
rainfall events, albeit with higher PPFD.
In addition to the very strong correlation between fog frequency and PPFD,
PPFD also correlated very strongly with total arboreal foliage area,
suggesting as possible relationship through limitations on the development
canopy substrata. While the mechanism for such a relationship remains
unclear, the observations contribute to the existing theory that the effect of
fog frequency on light conditions is one of the major drivers of variation in
tropical montane forest productivity.
La Cordillera Yanachaga es una cadena montañosa andina, semi-aislada por
extenderse en el territorio de la amazonia peruana. Alberga un área
importante de bosques montanos de niebla en sus flancos barlovento y
sotavento. A pesar de la importancia de estos bosques para la biodiversidad y
la provisión de servicios ecosistémicos a poblaciones cercanas, su variación
orográfica en clima y ecología no han sido descritas previamente. Se estudió
los parámetros climáticos y boscosos a lo largo de una gradiente orográfica
que consistió en tres sitios, bosque barlovento a 2400 msnm, bosque de
cresta a 2800 msnm y bosque sotavento a 2400 msnm. Se grabó mediciones
climáticas estándares y visibilidad desde torres del dosel dentro de parcelas
de vegetación de 1-ha, en las cuales se registraron datos ambientales y
caracteres taxonómicos, de follaje y estructurales de todos los tallos ≥5 cm
DAP.
A pesar de su ubicación orográfica, el bosque sotavento recibió levemente
menos lluvia que el bosque de cresta y una cantidad considerablemente
mayor al bosque barlovento. La variación en temperatura hallada se atribuyó
a la altitud y un efecto Foehn postmeridiano, mientras la variación orográfica
en radiación fotosintéticamente activa (RFA) fue altamente correlacionado a
la frecuencia de neblina. Los bosques de cresta y barlovento presentaron una
frecuente inmersión del dosel por neblina (c. 75%) y una mayor frecuencia
de eventos de neblina y lluvia simultanea, mientras el bosque sotavento
presentó menos inmersión por neblina (c. 20%) y mayor frecuencia de lluvia.
Los bosques de cresta y barlovento fueron afectados principalmente por
masas de aire orientales, mientras el bosque sotavento demostró señales de
un fenómeno localizado originado desde el valle de Oxapampa hacia el oeste.
El bosque sotavento presentó mas variación climática y mayores rangos de
parámetros, lo cual fue reflejado con mayor riqueza de especies, área basal,
altura del dosel, área del follaje y tamaño de hojas. Las asociaciones
florísticas dentro de las parcelas reflejaron sitios protegidos y expuestos.
Todos los bosques tuvieron densidades de tallos y áreas basales menores en
comparación con bosques comparables de otras regiones.
En el bosque sotavento, generalmente los eventos de neblina tenue y
moderada demostraron temperaturas y RFA con mayor semejanza a los
eventos de cielos despejados que a los eventos de lluvia, reflejando las
condiciones atmosféricas cálidas y despejadas en las que se forman. Los
eventos de neblina densa demostraron similitud a las condiciones
microclimáticas durante eventos de lluvia, aunque con mayor RFA.
En adición a la correlación muy fuerte entre frecuencia de neblina y RFA, RFA
también tuvo una correlación fuerte con el área total del follaje arbóreo,
sugiriendo una posible relación a través de limitaciones al desarrollo de
substratos en el dosel. Mientras que el mecanismo para la supuesta relación
no es claro, las observaciones contribuyen a la teoría existente que el efecto
de la frecuencia de neblina en las condiciones de luz es uno de los factores
claves para la variación en la productividad de bosque montano tropical.
... Epiphyte diversity has been documented at different scales, from point diversity (reference: single tree) to local diversity (reference: plot) to regional diversity (a series of plots along environmental gradients, regional species lists, and floras). The highest number of epiphyte taxa on a single tree ever reported is 190 species in a cloud forest in Peru ( Fig. 7.7, Catchpole and Kirkpatrick 2010). This number is really exceptional considering that the second and third highest reports "only" list 126 (Costa Rica) and 83 species (Bolivian). ...
... Outstanding point diversity. This 32 m tall emergent Ficus crassiuscula in a Peruvian cloud forest is host of a stunning 190 species of vascular epiphytes(Catchpole and Kirkpatrick 2010). Views of the tree crown from inside (a) and outside (b) (Photographs:Damian Catchpole) ...
The three-dimensional nature of epiphyte communities presents a challenge for access, data collection, and analysis. In the past, a majority of studies on epiphyte communities were purely descriptive and idiosyncratic, and this lack of theory and inconsistent methodology now hampers synthesis. However, recent progress in theory opens the possibility for major advances in the field in the near future. To date, we already know much of the structure, less though of the dynamics of epiphyte communities. Local diversity can be impressive with up to 190 species in a single tree. Although it is hardly conceivable that communities count with a similar number of distinct niches, there is good ecophysiological evidence for vertical stratification along steep environmental gradients from forest floor to upper canopy. The role of the host tree on species richness and abundance has been frequently studied, but we are still struggling with the development of appropriate null models to quantify the importance of host identity. Repeated inventories are rare; hence temporal changes are little documented and understood. This is true for both seasonal and interannual changes in relatively undisturbed vegetation as for forests affected by regular major disturbances, e.g., by tropical storms. Remarkably, the few cases of direct long-term observations indicate that epiphyte communities do not saturate even in mature lowland forest.
... The distribution of epiphytes throughout host plants can be influenced by abiotic factors such as humidity, luminosity and substrate (Benzing, 1987), as well as biotic factors, such as host plant characteristics, which can also influence the occupation and development of these organisms (Marcusso et al., 2019;Muller et al., 2019). A study by Catchpole and Kirkpatrick (2011) in Peru recorded the presence of 190 species of holoepiphytes and five hemiepiphytes in the canopy and trunk of a single strangler fig tree (Ficus crassiuscula Warb. ex Standl.) in a lowaltitude forest. ...
the Baturité Massif 62 species distributed in seven families (Araceae, Bromeliaceae, Cactaceae, Gesneriaceae, Orchidaceae, Piperaceae and Rubiaceae) were registered. Orchidaceae had the highest number of representatives (58%). The species Gomesa praetexta, Polystachya concreta and Trichocentrum cepula are new occurrences. Epidendrum anatipedium, E. sanchezii and Guzmania monostachia are endemic to Northeast Brazil. Vriesea baturitensis and V. carmeniae are endemic to the state of Ceará. Therefore, the Baturité Massif is an important area for biodiversity conservation.
... The distribution of epiphytes throughout host plants can be influenced by abiotic factors such as humidity, luminosity and substrate (Benzing, 1987), as well as biotic factors, such as host plant characteristics, which can also influence the occupation and development of these organisms (Marcusso et al., 2019;Muller et al., 2019). A study by Catchpole and Kirkpatrick (2011) in Peru recorded the presence of 190 species of holoepiphytes and five hemiepiphytes in the canopy and trunk of a single strangler fig tree (Ficus crassiuscula Warb. ex Standl.) in a lowaltitude forest. ...
... In many pristine tropical forests, vascular epiphytes are one of the most species-rich plant groups, with major impacts on nutrient and hydrological cycles in the ecosystem [9][10][11]. Epiphyte diversity can be impressive, e.g., a single tree may harbour almost 200 vascular epiphyte species [12]. However, epiphyte richness in human-modified landscapes is usually substantially reduced (see [13,14]). ...
Ongoing destruction of tropical forests makes isolated pasture trees potentially important for the persistence of original forest dwellers such as many vascular epiphytes. We studied epiphyte assemblages on 100 isolated trees at ten pasture sites in southwest Panama along an elevational gradient ranging from 140 to 1240 m a.s.l. We analysed epiphyte species composition (richness, similarity) and registered climate and host trait variables of potential influence on their occurrence. We found a total of 5876 epiphyte individuals belonging to 148 species. Epiphyte abundance, species richness and diversity all varied about 4-fold among the 10 sites, with a high similarity of epiphyte assemblages among sites. Two sites at 870 and 1050 m a.s.l. did not fit into the overall elevational trend of increased abundance, species richness and diversity. However, all three measures were significantly correlated with humidity as the independent variable. This highlights that a gradient in humidity, and not elevation as such, is responsible for the typical elevational changes in epiphyte assemblages, so that special local conditions may lead to deviations from expected patterns. Our documentation of current elevational diversity patterns also provides a baseline for the study of long-term changes in epiphyte assemblages in anthropogenically modified landscapes.
... One of the most conspicuous features of tropical montane cloud forests (TMCFs) is their rich and abundant epiphyte communities (Bruijnzeel, Scatena, & Hamilton, 2011;Foster, 2001;Gentry & Dodson, 1987;Zotz, 2016). Individual trees support up to 190 species (Catchpole & Kirkpatrick, 2011), and stands accumulate up to 44 t/ha of epiphytic material (Gotsch, Nadkarni, & Amici, 2016). Epiphytes may contribute 50% of the within-crown leaf area of tropical forests (Hofstede, Wolf, & Benzing, 1993). ...
Tropical montane cloud forests support abundant epiphytic vascular plant communities that serve important ecosystem functions, but their reliance on atmospheric inputs of water may make them susceptible to the drying effects of rising cloud bases and more frequent droughts. We conducted a common garden experiment to explore the combined effects of decreasing cloud influence—lower humidity, warmer temperature, brighter light—and meteorological drought (i.e. absence of rain) on the physiology and morphology of vascular epiphytes native to primary forests of Monteverde, Costa Rica. The epiphytes, which exhibited C3 photosynthesis, were sourced from a lower montane cloud forest (CF) or a rainforest (RF) below the current cloud base and transplanted into nearby shadehouses (CF or RF shadehouse respectively). Vapour pressure deficit (VPD) and light availability, measured as photosynthetically active radiation, were 2.5 and 3.1 times higher in the RF than the CF shadehouse. Half of the plants were subjected to a severe 4‐week drought followed by a recovery period, and the other half were watered controls. Plants subjected to low VPD/light conditions of the CF shadehouse were physiologically and morphologically resistant to the drought treatment. However, compared to control plants, both sources of plants subjected to high VPD/light conditions of the RF shadehouse experienced declines in maximum net photosynthesis (Amax), stomatal conductance (gs) and the proportion of healthy leaves (those not exhibiting chlorosis, desiccation or necrosis). At peak drought, leaves from the RF were 19% thinner than controls. Within 7–14 days after rewatering, Amax, gs and leaf health recovered to nearly the levels of controls. Growth rate, mortality and phenology were unaffected by the treatments. The divergent responses to drought in the CF versus RF shadehouses, combined with the recovery in the RF shadehouse, indicate that these epiphytes possess adaptive properties that confer low resistance, but high recovery capacity, to episodes of short‐term drought over a range of cloud influence. In addition, the reduction in Amax suggests stomatal regulation that favours water conservation over carbon acquisition, a strategy that may inform epiphyte responses to rising clouds and increasing drought frequency expected in the long term. A free Plain Language Summary can be found within the Supporting Information of this article. A free Plain Language Summary can be found within the Supporting Information of this article.
... During host tree ontogeny, the total bark area as well as the environmental heterogeneity increases as a function of tree architecture, growth rate and crown dynamics (Einzmann, Beyschlag, Hofhansl, Wanek, & Zotz, 2014;Flores-Palacios & García-Franco, 2006;Sarmento Cabral et al., 2015;Wagner & Zotz, 2020;Zotz & Vollrath, 2003). The characteristics of host individuals in combination with the vertical stratification of the forest stand may allow for an impressive number of epiphyte species to coexist in a single tree (Hietz, Winkler, Scheffknecht, & Hulber, 2012;Petter et al., 2016;Ruiz-Cordova, Toledo-Hernández, & Flores-Palacios, 2014), the record being over 200 species found on a single tree in a cloud forest in Peru (Catchpole & Kirkpatrick, 2011). Nevertheless, the lack of comparative studies makes it difficult to assess whether major drivers of local species richness are consistent across regions. ...
Vascular epiphytes are a diverse and conspicuous component of biodiversity in tropical and subtropical forests. Still, the patterns and drivers of epiphyte assemblages are poorly studied in comparison to soil‐rooted plants. Our current knowledge about diversity patterns of epiphytes mainly stems from local studies or floristic inventories, but this information has not yet been integrated to understand large‐scale distribution patterns better. EpIG‐DB, the first database on epiphyte assemblages at the continental scale, results from an exhaustive compilation of published and unpublished inventory data from the Neotropics. The current version of EpIG‐DB consists of 463 196 individual epiphytes from 3005 species, which were collected from a total of 18,148 relevés (host trees and “understory” plots). EpIG‐DB reports the occurrence of “true” epiphytes, hemi‐epiphytes and nomadic vines, including information on their cover, abundance, frequency and biomass. Most records (97%) correspond to sampled host trees, 76% of them aggregated in forest plots. The data is stored in a TURBOVEG database using the most up‐to‐date checklist of vascular epiphytes. For the standardization of associated data commonly used in epiphyte ecology, e.g. by considering different sampling methods, 18 additional fields were created. EpIG‐DB currently covers six major biomes across the whole latitudinal range of epiphytes in the Neotropics but welcomes data globally. This novel database provides, for the first time, unique biodiversity data on epiphytes for the Neotropics and unified guidelines for future collection of epiphyte data. EpIG‐DB will allow to explore new ways of studying the community ecology and biogeography of vascular epiphytes.
... Tropical forests are characterized by extremely high biodiversity, endemism and life forms (Bossuyt et al. 2004;Mittermeier et al. 1998). More than 300 tree species may be found in a single hectare of forest (Balslev et al. 1998), and a single tree may in extreme cases be inhabited by almost 200 species of vascular epiphytes (Catchpole and Kirkpatrick 2010). Epiphytes are plants that grow on other plants, not parasitically but for support (Benzing 1990) and are generally restricted to humid environments, reaching their greatest diversity and abundance in wet regions in the tropics (Reinert 1998). ...
Aims
Epiphytes and hemiparasites do not have direct access to soil nutrients. Epiphytes acquire nutrients through symbiosis, foliar leachates and throughfall, whilst hemiparasites have specialized structures (haustoria) to acquire nutrients from their host. Irrespective of the green leaf nutrient concentrations of epiphytes, hemiparasites and their hosts, nutrient-resorption efficiency and proficiency are expected to be the greater in epiphytes than in their hosts and in hemiparasites. These hypotheses were tested.
Methods
Green and senescing leaves of epiphytes (n = 23), hemiparasites (n = 9) and their hosts were collected, and leaf area, leaf dry weight, nutrient (nitrogen-N, phosphorus-P, potassium-K, calcium-Ca) and sodium (Na) concentrations were measured, and resorption efficiency (%) and proficiency were calculated.
Important Findings
Concentrations of N, P, K, Ca and Na in green leaves of epiphytes and hemiparasites were either similar or greater than those of their hosts, except for lower green leaf N concentration in hemiparasites. Epiphytes resorbed N, P, K and Na, while their hosts resorbed only N, P and K. Hemiparasites and their hosts resorbed P, K and Na while N was not resorbed. Overall, resorption efficiency was greatest in epiphytes > hemiparasites = hosts, while the resorption proficiencies were similar or greater for epiphytes and hemiparasites compared with their hosts, except for N in hemiparasites. Relatively high nutrient concentrations in epiphytes were associated with greater resorption efficiency. Understanding contrasting nutrient concentrations in epiphytes, hemiparasites and their hosts will be important in recognising their contribution to ecosystem nutrient cycling.
... The epiphytes are an important group in the tropical montane cloud forest and are crucial for the diversity of other organisms (Nadkarni & Matelson 1989). The orchids and pteridophytes in particular contribute the greatest richness to the epiphyte flora (Barthlott et al. 2001, Bøgh 1992, Catchpole & Kirkpatrick 2010, Kelly et al. 1994. The species of these groups that were found are xerotolerant and it is likely that the most sensitive taxa either require a longer time period to recover or do not establish at all. ...
... única árvore pode servir de suporte para 126 (Schuettpelz & Trapnell, 2006) a 195 espécies de epífitas vasculares (Catchpole & Kirkpatrick, 2011), embora valores menores já sejam considerados altos, como cerca de 80 epífitas vasculares por árvore Krömer et al., 2005;Petean, 2009). Esta elevada diversidade torna a forma de vida um tema atraente e ao mesmo tempo complexo para estudos ecológicos. ...
... The epiphytes are an important group in the tropical montane cloud forest and are crucial for the diversity of other organisms (Nadkarni & Matelson 1989). The orchids and pteridophytes in particular contribute the greatest richness to the epiphyte flora (Barthlott et al. 2001, Bøgh 1992, Catchpole & Kirkpatrick 2010, Kelly et al. 1994. The species of these groups that were found are xerotolerant and it is likely that the most sensitive taxa either require a longer time period to recover or do not establish at all. ...
The response of vascular epiphyte communities following natural or human disturbance has been little studied. Over 5 y, we evaluated the post-stripping recolonization of vascular epiphytes in cloud forest. Vascular epiphytes were experimentally removed from branch and trunk plots (1 m in length) on five trees in two secondary cloud forest fragments in southern Mexico. Similarity between colonizer and established communities was compared in each fragment using a further five trees with no stripping. All seedlings were recorded yearly. Non-vascular epiphyte cover was estimated in each plot. The recolonization rate was very high; after 5 y, epiphyte density of the colonizer community (27.4 ± 6.8 individuals per segment) reached similar values to those of the established community (26.7 ± 3.3) in nearby trees. While similarity (composition and abundance) between the colonizer community and established community was high (81%), diversity accumulation curves indicated that the colonizer community presents a lower diversity of epiphytes (5.5 equivalent species) than the established community (11.4). Colonization of xerophytic bromeliads was high, while pteridophytes and orchids presented reduced recovery. The immediately surrounding source of propagules had a strong influence on recolonization. In both the colonizer and established communities, dominance rank was bromeliads > peperomias > pteridophytes. The results show that the recovery capacity of epiphytic vegetation in secondary forest is high, if propagule sources are close by. However, at 5 y after disturbance, it is unclear whether the colonizer community would present the same species composition as the established community or if it would give rise to a different community.
... Tropical forests are characterized by an unmatched diversity of organismal forms. More than 300 tree species may be found in a single hectare of forest (Balslev et al. 1998); and a single tree may in the extreme case be inhabited by almost 200 species of vascular epiphytes (Catchpole and Kirkpatrick 2010). Currently, studies on processes that shape tropical plant communities show a very strong bias towards a single life form, i.e. trees (e.g. ...
The processes which govern diverse tropical plant communities have rarely been studied in life-forms other than trees. Structurally dependent vascular epiphytes, a major part of tropical biodiversity, grow in a three-dimensional matrix defined by their hosts, but trees differ in their architecture, bark structure / chemistry and leaf phenology. We hypothesized that the resulting seasonal differences in microclimatic conditions in evergreen vs. deciduous trees would affect epiphytes at different levels, from organ physiology to community structure. We studied the influence of tree leaf phenology on vascular epiphytes on the Island of Barro Colorado, Panama. Five tree species were selected, which were deciduous, semi-deciduous or evergreen. The crowns of drought-deciduous trees, characterized by sunnier and drier microclimates, hosted fewer individuals and less diverse epiphyte assemblages. Differences were also observed at a functional level, e.g. epiphyte assemblages in deciduous trees had larger proportions of CAM species and individuals. At the population level a drier microclimate was associated with lower individual growth and survival in a xerophytic fern. Some species also showed, as expected, lower SLA and higher δ(13)C values when growing in deciduous trees compared to evergreen trees. As hypothesized, host tree leaf phenology influences vascular epiphytes at different levels. Our results suggest a cascading effect of tree composition and associated differences in tree phenology on the diversity and functioning of epiphyte communities in tropical lowland forests.
Urban ecosystems could jeopardize the existence of vascular epiphytes (VS), given that their occurrence is linked to phorophyte availability and particular climatic conditions. Despite reports of VS in cities, nothing is known about their demography. A first step in this direction is to describe their population structures (PS). We established the PS of VS present in urban parks in Oaxaca City, addressing the following questions: what is their demographic status? and are there differences in the structure of populations growing in native versus exotic phorophytes? During 2021, we censused all the trees in six urban parks, recording their origin (native or exotic), the epiphytic species found on them and the development stages present in each VS population. Overall, five VS species were documented: Tillandsia ionantha , T. makoyana , T. sp , T. recurvata and T. schiedeana ; the first three with only one individual and the latter two with 5,694 and 95, respectively. A MANOVA test indicated significant differences in PS between T. recurvata (type I structure, suggesting a growing population) and T. schiedeana (type III structure, suggesting a senile population) (Wilkes' λ = 0.821, F-Radio = 11.96 P < 0.001). PS showed no differences related to tree origin. Our results indicate that it is necessary to conduct demographic studies to have a more accurate idea of the current condition of vascular epiphytes in cities. For instance, even though we found five VS species, only one of them seems to have viable populations in Oaxaca city.
ContextHuman-driven landscape processes such as habitat loss and fragmentation act on biodiversity but their effects are mediated by spatial scale. Quantification of the effects of the spatial scale of landscape processes on biodiversity moves beyond a purely ecological concern, towards a pragmatic tool for conservation aiming to designing biodiversity-rich landscapes.Objectives
We conducted a multiscale study to quantify the direction of effect (positive, negative, or neutral) and spatial scale (scale of effect, SoE) that three landscape processes—habitat loss (forest cover), fragmentation (number of patches), and edge effects (edge density)—exert independently on epiphyte biodiversity. Methods
We focused on hyperdiverse vascular epiphytes and orchid communities, sampled across 23 human-modified landscapes in the mountainous region of the eastern Colombian Andes. We consider 12 spatial scales ranging from 100-2400 m radii and use metrics of Hill numbers to quantify biodiversity responses. ResultsHabitat loss and edge effects act at fine spatial scales (SoE= 200 m radius), predicting low species richness and abundance distributions across epiphytes and orchid communities. Fragmentation negatively impacts orchid communities at coarse scales (SoE= 2400 m radius). However, the biodiversity-landscape relationship might be undetected if assessed at the incorrect spatial scales (Forest cover 800-1500 m; Fragmentation ≥ 300 m; and edge density ≤800 radii).Conclusions
We showed that habitat loss, fragmentation, and edge effects all play a negative role on biodiversity, and their detectability and impact is scale dependant. To design landscapes that are beneficial for mountainous plant biodiversity, it is important to improve forest cover as well as to reduce fragmentation and edge effects.
Factors controlling holoepiphyte (plants which start and complete their life cycle on a phorophyte) distributions may be wide and variable. They are determined either by spatial processes, as evidenced by dispersal limitation and/or historical factors, environmental filters, such as microsite variation within phorophytes, and/or biotic interactions. Disentangling the importance of these classes is particularly difficult in tropical forests where phorophyte alpha-diversity is exceptionally high. We controlled for phorophyte specificity by studying the holoepiphytic communities of an emergent tree Aldina heterophylla (Fabaceae), known for its heavy epiphyte loads and dominance in Amazonian white-sand habitats, in order to quantify the importance of tree zone and geographic distance on holoepiphytes at fine (100 m2) and regional (2500 km2) scales. At regional scales, tree zone explained nearly two-thirds of the main compositional gradient, accounting for more than double that of site differences. No spatial effects were observed on holoepiphyte community structure at the fine scale as treelet communities were more dissimilar than by chance alone from their neighboring emergent phorophyte. These results suggest that microsite availability, as opposed to dispersal limitation, is the most important mechanism in structuring holoepiphyte communities of this insular forest type.
Cloud-water and rainfall interception are hydrological processes of particular interest in Tropical Montane Cloud Forests (TMCF). Studies in these systems have shown important contributions of cloud/fog water to the hydrological balance. To evaluate the importance of cloud/fog water to montane forests of the western slope of the Cordillera Yanachaga in the eastern Andes of central Peru, we monitored bulk precipitation (gross rainfall), cloud water and net precipitation weekly over one year at two elevations, 2468 and 2815masl. Bulk precipitation was greater at the upper site (2753mm) than at the lower site (2222mm). Annual net precipitation was 92.4% and 70.4% of rainfall at the upper and lower sites, respectively. Net precipitation was primarily composed of throughfall; stemflow was negligible, contributing less than 0.2% of annual rainfall at both sites. Apparent annual rainfall interception losses by the canopy were 7.7% and 29.6% of the bulk precipitation at the upper and lower sites, respectively. Apparent weekly rainfall interception at the upper site was sometimes negative and lower compared to that of the lower site. Apparent cloud-water interception occurred at least during weeks when negative rainfall interception was recorded, a contribution of 21mm (0.8% of the annual rainfall) at the upper site. However, the apparent low rainfall interception losses at the upper site suggest that canopy wetting and subsequent saturation by cloud/fog water during periods with apparent positive rainfall interception may have contributed a difference of ca. 22% of apparent rainfall interception losses between sites. These contributions were supported by maximum apparent fog interception recorded by a fog gauge at the upper site. Although other equally important factors like topography, crown exposure and mossiness were not evaluated, the quantity of apparent fog interception at the upper site was found related to the canopy leaf area index. This important relationship has been previously described but mostly overlooked in studies of TMCF.
Epiphyte diversity as well as distribution and composition of epiphytic biomass was investigated in two lowland and two montane rain forests in Ecuador. Species numbers of epiphytes per tree were slightly higher in the montane (22–41 in Los Cedros, 33–54 in Otonga) than in the lowland forests (9–43 in Yasuni, 19–32 in Tiputini), however differences were not significant. In contrast, some epiphyte families did show significant altitudinal differences. The total epiphytic biomass per branch surface decreased from the centre of the crown to the periphery, and was generally higher in the montane (6.0 kg m−2 on central branches in Los Cedros, 1.8 kg m−2 in Otonga) than in the lowland forests (1.3 kg m−2 in Yasuni and 1.8 kg m−2 in Tiputini). Especially, dry weight of bryophytes and dead organic matter was higher in the mountains. In contrast, the biomass of green parts of vascular epiphytes on central branches was about the same in all four forests (0.4–0.6 kg m−2). A comparison with literature data from other study sites of tropical moist forests supports the observation that biomass of vascular epiphytes does not significantly change with altitude. It is discussed, that the high bryophytic biomass in montane compared to lowland forests is a major reason for differences in humus biomass between these forest types.
The sensitivity of pollen as an indicator of elevation in neotropical lowland and Andean forests was measured using modern pollen samples collected from moss-polsters along a transect between 340 m and 3530 m elevation and from surface sediments in lowland swamps (240 m) of Madre de Dios, Peru. A blind study, using samples collected from the same transect in the following year, provided a test of reproducibility. The results show (1) clear elevational distribution patterns and (2) the ability of calibration data to predict the altitude of the blind samples. Characteristic associations of pollen taxa are found under differing hydrologies and elevations. The floodplain pollen assemblages are characterized by abundant Mauritia, Sloanea, Ficus, Iriartea and Arecaceae pollen types. At higher elevations, these lowland types decrease or are absent. Alchornea, Urticaceae/Moraceae, Bignoniaceae and Cecropia are dominant components of the pollen rain of the low-elevation zone (<1000 m). Acalypha, Alchornea, Cecropia, Rubiaceae and Urticaceae/Moraceae are important between 1000 m and 1600 m elevation. Pollen of Hedyosmum, Alnus, Poaceae and Combretaceae/Melastomataceae are abundant between 1600 m and 2000 m. Cecropia pollen dominates samples from low- to mid-elevation disturbed forests. Alnus pollen is most abundant, and Poaceae becomes rare, between 2000 and 2700 m. At high elevations above 2700 m, Asteraceae, Poaceae, Polylepis, Muehlenbeckia-type and Myrsine pollen are dominant. Statistical analysis of the data set using Detrended Correspondence Analysis (DCA) shows a precise correlation between community composition and elevation. The DCA axis 1 values are strongly correlated with sample elevation, exhibiting a linear relationship (r2=0.904). The results provide an estimate of the sensitivity of pollen analysis in the Neotropics as a proxy for measuring elevation and, by inference, temperature.
An exhaustive survey of vascular epiphytes on a single mature canopy tree in a Costa Rican tropical premontane wet forest revealed an extraordinary level of epiphyte diversity. A total of 126 mor-phospecies representing at least 52 genera and 21 plant families were found growing epiphytically on the phorophyte (host tree), accounting for more than 1% of the entire vascular flora of Costa Rica. This is considerably higher than most other epiphyte surveys of single trees. Angiosperms accounted for 64% of the species while leptosporangiate ferns accounted for 36%. Consistent with earlier studies, orchids con-tributed less than would be expected from their global representation, while ferns contributed more signif-icantly to species diversity. Fewer species were found on the tree trunk (58 species) than in the crown (85 species), and little species overlap occurred between these two regions (17 species), suggestive of niche partitioning. Three species and 11 individuals per m 2 were recorded on the trunk of the phorophyte. Our results underscore the important contributions of epiphytes to overall biodiversity, and highlight the neces-sity of including epiphytes in future biodiversity assessments.
High diversity and abundance of epiphytes are one of the special characteristics of tropical montane cloud forests. Although epiphytes, apart from their important. role as structural elements in this ecosystem, play an important role in the hydrological balance, few detailed studies on epiphyte vegetation exist. In the area of Reserva Biologica San Francisco in Southern Ecuador, a detailed inventory of the epiphytes along four altitudinal transects at 1800-3150m was carried out. The research area holds one of the most species-rich epiphyte floras in the world. So far at least 627 epiphyte species have been recorded. Monocoryledons are most important, with orchids alone accounting for 50% of all species. Species numbers change considerably along the altitudinal gradient. In the lower montane forest between 1850 and 2100 m, 340 epiphyte species were recorded, compared with 283 in the upper montane forest (2100-2450 m), 120 in the subalpine elfin forest (24.50-2650 m), and only four species in Paramo areas above the timberline. The highest epiphyte diversity can always be found in the uppermost branch area of the tree canopy. This zone is particularly colonized by orchids, and in contrast to other tropical montane forests, bromeliads, ferns and Ericaceae can be found abundantly in this zone too. All other families colonize mainly the lower stem zone. Accepted 16 August 2001.
The mobile crane of the Surumoni project allowed for the first time ever a complete inventory and spatial description of the epiphytic vegetation of a tropical lowland rain forest plot (1.5 ha), at La Esmeralda on the upper Orinoco River, Venezuela. A total of 778 individual vascular epiphytes of 53 species was found, dominated by 19 orchid species and 14 species of Araceae. Fifty percent of all individual plants were obligate ant-garden epiphytes. The distribution of epiphytes was highly clumped and not random. The clumped occurrence of holoepiphytes (complete life cycle on host tree) was the consequence of the rarity of suitable phorophytes (host trees; e.g., size and age) in the plot and the preference of ants for gaps where most of the ant-garden epiphytes were found. In comparison, hemiepiphytes were distributed more evenly because of greater independence from tree suitability. The dispersal modes of epiphytes did not explain their distribution patterns. There was no consistent difference in distribution between anemochorous and zoochorous epiphytes, presumably because availability of suitable substrate is the more important factor for epiphyte establishment and growth. Whereas the vertical distribution of epiphytes could be attributed largely to deterministic factors such as physiological adaptation and requirements, horizontal distribution appeared to be governed by suitable substrate, which in turn seemed to be governed by stochastic gap formation.
Aim To document the elevational pattern of epiphyte species richness at the local scale in the tropical Andes with a consistent methodology.Location The northern Bolivian Andes at 350–4000 m above sea level.Methods We surveyed epiphytic vascular plant assemblages in humid forests in (a) single trees located in (b) 90 subplots of 400 m2 each located in (c) 14 plots of 1 ha each. The plots were separated by 100–800 m along the elevational gradient.Results We recorded about 800 epiphyte species in total, with up to 83 species found on a single tree. Species richness peaked at c. 1500 m and declined by c. 65% to 350 m and by c. 99% to 4000 m, while forests on mountain ridges had richness values lowered by c. 30% relative to slope forests at the same elevations. The hump-shaped richness pattern differed from a null-model of random species distribution within a bounded domain (the mid-domain effect) as well as from the pattern of mean annual precipitation by a shift of the diversity peak to lower elevations and by a more pronounced decline of species richness at higher elevations. With the exception of Araceae, which declined almost monotonically, all epiphyte taxa showed hump-shaped curves, albeit with slightly differing shapes. Orchids and pteridophytes were the most species-rich epiphytic taxa, but their relative contributions shifted with elevation from a predominance of orchids at low elevations to purely fern-dominated epiphyte assemblages at 4000 m. Within the pteridophytes, the polygrammoid clade was conspicuously overrepresented in dry or cold environments. Orchids, various small groups (Cyclanthaceae, Ericaceae, Melastomataceae, etc.), and Bromeliaceae (below 1000 m) were mostly restricted to the forest canopy, while Araceae and Pteridophyta were well represented in the forest understorey.Main conclusions Our study confirms the hump-shaped elevational pattern of vascular epiphyte richness, but the causes of this are still poorly understood. We hypothesize that the decline of richness at high elevations is a result of low temperatures, but the mechanism involved is unknown. The taxon-specific patterns suggest that some taxa have a phylogenetically determined propensity for survival under extreme conditions (low temperatures, low humidity, and low light levels in the forest interior). The three spatial sampling scales show some different patterns, highlighting the influence of the sampling methodology.
Aim We aim to assess regional patterns in the distribution and species richness of vascular epiphytes with an emphasis on forests that differ in altitude and the amount of rainfall.
Location Tropical America, in particularly the 75,000 km2 large state of Chiapas in southern Mexico at 14.5–18.0°N. Chiapas is diverse in habitats with forests from sea-level to the tree-line at c. 3800 m altitude and with annual amounts of rainfall ranging from 800 to over 5000 mm. It is also one of the botanical best-explored regions in the tropics.
Methods First we give an overview of epiphyte inventories to date. Such epiphyte surveys were mostly carried out on the basis of surface area or individual trees and we discuss their problematic comparison. Applying a different methodological approach, we then used 12,276 unique vascular epiphyte plant collections from Chiapas that are deposited in various botanical collections. The locality data were georeferenced and compiled in a relational data base that was analysed using a geographical information system. To compare the number of species between inventories that differed in the numbers of records, we estimated the total richness, SChao, at each.
Results We recorded 1173 vascular epiphyte species in thirty-nine families (twenty-three angiosperms), comprising c. 14% of all confirmed plant species in the state. About half of all species were orchids (568). Ferns and bromeliads were the next species-rich groups with 244 and 101 species, respectively. Most species were found in the Montane Rain Forest and in the Central Plateau. Trees of different forest formations, rainfall regimes, altitudes and physiographical regions supported a characteristic epiphyte flora.
Main conclusions We were able to confirm the presumed presence of a belt of high diversity at mid-elevations (500–2000 m) in neotropical mountains. In contrast to predictions, however, we observed a decrease in diversity when the annual amount of rainfall exceeded 2500 mm. The decrease is attributed to wind-dispersed orchids, bromeliads and Pteridophyta that may find establishment problematical under frequent downpours. In the wet but seasonal forests in Chiapas, this decrease is not compensated by plants in the animal-dispersed Araceae that are abundant elsewhere. We presume that in addition to the annual amount of rainfall, its distribution in time determines the composition of the epiphyte community.
Species diversity of vascular epiphyte plant communities was studied in La Carbonera, a montane rain forest dominated by Podocarpaceae in the Venezuelan Andes. We compared the epiphyte communities of the primary, disturbed, and secondary forest areas of La Carbonera in order to augment the scarce knowledge on the effects of anthropogenic disturbance on these important elements of tropical vegetation. Diversity of vascular epiphytes (191 species in the whole forest area) was low in the disturbed and secondary areas (81 spp.) compared to adjacent primary forest (178 spp.). Four types of disturbed forest and secondary vegetation supported different numbers of epiphyte species, showing a decline with increasing degrees of disturbance (65 spp. along a road transect, 42 spp. on relict trees in disturbed forest, 13 spp. in a tree plantation and 7 spp. in a former clearing, both secondary vegetation units). Epiphytic species composition in primary and disturbed or secondary forest areas differed markedly: disturbed habitats harboured fewer fern and orchid species but more bromeliad species than the primary forest. Probably the families occurring only in primary forest sites of our study may be useful as bioindicators to determine the degree of disturbance in other habitats of mountain rain forests as well. Epiphyte abundance was also lower in disturbed habitats: a remnant emergent tree supported only about half as many epiphyte individuals as a member of the same species of similar size in the primary forest. The decrease in species numbers and abundance as well as the differences in species composition are mainly due to the less diverse phorophyte structure and less differentiated microclimate in the disturbed and secondary vegetation compared to the primary forest.
About ten percent of all vascular plant species world-wide are epiphytes and they are almost exclusively found in tropical forests. Therefore, they constitute a large part of the global plant biodiversity (10% of all species), and in tropical countries represent up to 25% of all vascular plant species. Focusing on the differences between epiphytes in the strict sense or holo-epiphytes (non-parasitic plants that use other plants – usually trees – as growing sites all through their life-cycle) and hemi-epiphytes (half epiphytes which only spend part of their life as epiphytes until their aerial roots become connected to the ground), horizontal and vertical distribution patterns of both in relation to some of their ecological requirements are compared. Vertical ecological gradients (i.e., insolation and humidity differences from the forest floor to the canopy surface) are relevant for the composition of the holo- epiphytic vegetation. For hemi-epiphytes, however, ecological differences between distinct forest habitats (i.e., horizontal gradients) are relevant, but not primarily the canopy structure, as the individual host tree structure is more important. The scale-dependence of epiphyte diversity assessment (relatively small study areas for holo-epiphytes, large study areas for hemi-epiphytes) is mainly due to the striking differences in plant sizes and related mechanical and physiological requirements.
Using the data published in the Catalogue of the Flowering Plants and Gymnosperms of Peru, we analyzed the elevational distributions of 5323 species reported as endemics from that country as a whole, for 10 families with the highest number of endemic taxa in Peru, and the distribution patterns of these species according to life form. We calculated the density of endemism (number of endemic species divided by area 1000) and absolute number of endemic species among life forms and families, along an elevational gradient. Overall densities of endemics were 10–15 times higher at mid-elevation (2000–3500 m) than in the Amazonian lowlands (0–500 m). Absolute numbers of endemics peaked at 1500–3000 m for herbs, shrubs, and epiphytes, while trees, vines, and lianas showed maxima in the lowlands (0–500 m); yet densities of endemics for all life forms peaked at 1500–3000 m. Among the 10 families with the highest number of endemics, densities of endemics peaked at mid- to high elevation (1500–4500 m), but showed much disparity in the elevational distribution of absolute numbers of endemic species. Finally, the percentage of endemic species to total species is highest for herbs, shrubs, and epiphytes. Given that less than 10% of the land area for each of the montane zones (2000–4500 m) is protected compared to 13.5–29.9% in the lower elevations (0–1000 m), we recommend that priority be given to increasing the size of protected areas at mid- to high altitude in the Andean slopes to grant further protection in zones with the highest density of endemics. We also recommend that more emphasis be given to collecting and studying non-trees, since most endemic species belong to that class.
The design and implementation of conservation plans for the humid montane forests (including tropical montane cloud forests—TMCFs) of Peru require information about the physical and social parameters that result in or limit the distribution, physiognomy, species composition, and diversity of those forests. Obvious physical factors include the extent and connectivity of the elevational zones where these forests are found, climatic regimes, and edaphic limitations. These in turn set the stage for ecological and evolutionary processes that influence the types of species present (e.g., whether or not there are endemics, habitat specialists, or organisms with poor dispersal abilities). Human population densities and trends (e.g., population increase, immigration/ emmigration) have strong, but not necessarily simple, relations to the degradation of natural resources (Harrison 1991). The current living standards and future aspirations of people provide a context for making predictions. Change, however, can only be induced by first recognizing the social actors (or “stakeholders”) most directly involved in natural resource degradation or conservation (Garcia-Guadilla 1992).
We report the results of the first complete samples of all plant species and individuals for any lowland tropical forest in the world. The three forests sampled are in western Ecuador; Rio Palenque, Jauneche, and Capeira are, respectively, wet, moist, and dry forests. In each forest we sampled all vascular plants in a 0.1-ha area. At wet forest Rio Palenque, nontree habit groups make up most of the sampled species and individuals. Over a third of the species and almost half the individual plants are epiphytes, 13 percent of the species are terrestrial herbs, 10 percent are shrubs, and 9 percent nonepiphytic climbers. The moist and dry forest samples have many fewer species, largely due to many fewer epiphytes. The new data are compared with the most diverse 0.1-ha samples from elsewhere in the world. Our wet forest sample is by far the most species-rich such sample yet recorded and would remain so even if all tree species were excluded from the data.
The distribution of vascular epiphytes was analyzed on three emergent trees (Hura crepitans, Ceiba pentandra, and Couratari stellata). A total number of 77 species, including 46 orchids, in 17 families was recorded. Number of species was highest in the center of the tree crowns while cover was highest in the middle third of the crown or equally distributed. This leads to the assumption that succession does not always reach equilibrium on old branches towards crown center. Distribution patterns of single species do not necessarily correspond to that of the total epiphyte mass. The entire epiphyte cover is highest on the top of branches while certain species, that could be discussed as specialists on the basis of particular life-form characteristics, are equally abundant on the bottom. There was no clear distribution pattern with respect to branch inclination. Distribution patterns are partly explained by the life-form of the plants.
A method of climbing into the canopy of tall trees is described, using equipment which does not damage the tree and which can be carried by a single person.
The vascular flora of 1.5 ha of montane rain forest on a ridge top at 2550-2650 m near Merida, Venezuela was surveyed, compared with other montane forests in the region, and analysed to determine its biogeographic origins and affinities. The study included an inventory of all stems greater-than-or-equal-to 3.2 cm d.b.h. in eighteen 12 x 12 m plots. The canopy was 10-22 m tall and the trees relatively small (3488 individuals ha-1, basal area 34.7 m2 ha-1). Bamboos were abundant in gaps, there were no buttressed trees and relatively few climbers. Weinmannia glabra L.f. (Cunoniaceae), Clusia trochiformis Vesque (Guttiferae) and Hedyosmum creantum Occhioni (Chloranthaceae) together accounted for 42% of the individuals and 37% of the basal area. Microphylls, notophylls and mesophylls predominated in the leaf size spectrum. Overall, 219 vascular plant taxa were distinguished in the 1.5 ha study area, including forty-four tree species (plus c. eight Lauraceae), fifteen shrubs, twenty-six herbs (including terrestrial ferns), twenty-one climbers, eight hemiepiphytes, 120 true epiphytes and four hemiparasitic epiphytes (many species occurred as more than one life form). Orchidaceae (sixty-five species), Bromeliaceae (fourteen) and Rubiaceae (eleven) were the best-represented families. The proportion of true epiphytes in the total flora (50%) exceeds estimates published for other sites. Forty-four per cent of the flora of the study area is restricted to northern Venezuela and Colombia, 25% is endemic to Venezuela and 7% is endemic to Merida state. The flora is thus more geographically specialized than those of isolated montane forests at lower altitudes near the Caribbean coast. The majority of the flora (65%, principally epiphytes) had wind-dispersed diaspores (dust, comose, winged) and 29% of the species (including most trees and shrubs) had succulent fruits. The species with succulent fruits had more limited distributions than the wind-dispersed species. The forest of the study site is floristically distinct from even the nearest other studied montane forests. Future studies should examine whether inter-site differences in montane forests are greater than those between lowland sites separated by similar distances.
Vascular epiphytes were studied in forests at alti-tudes from 720 to 2370 m on the Atlantic slope of central Veracruz, Mexico. The biomass of all trees of each species > 10 cm diameter at breast height within plots between 625 and 1500 m 2 was estimated. The number of species per plot ranged between 22 and 53, and biomass between 9 and 249 g dry weight/m 2 . The highest values, both of species and biomass, were found at an intermediate altitude (1430 m). Habitat diversity may contribute to epiphyte diversity in humid for-ests, but the importance of this effect could not be distin-guished from the influence of climate. A remarkably high number of bromeliads and orchids grew in relatively dry forests at low altitudes. In wet upper montane forests, bromeliads were replaced by ferns, while orchids were numer-ous at all sites, except for a pine forest. The number of epiphytic species and their biomass on a tree of a given site were closely related to tree size. According to Canonical Correspondence Analysis, the factor determining the compo-sition of the epiphytic vegetation of a tree was altitude and to some extent tree size, whereas tree species had practically no influence. The only trees which had an evidently negative effect on epiphytes were pines, which were particularly hostile to orchids and to a lesser degree to ferns, and Bursera simaruba, which generally had few epiphytes due to its smooth and defoliating bark.
Part 1. It is shown that in a large collection of Lepidoptera captured in Malaya the frequency of the number of species represented by different numbers of individuals fitted somewhat closely to a hyperbola type of curve, so long as only the rarer species were considered. The data for the commoner species was not so strictly `randomized', but the whole series could be closely fitted by a series of the logarithmic type as described by Fisher in Part 3. Other data for random collections of insects in the field were also shown to fit fairly well to this series. Part 2. Extensive data on the capture of about 1500 Macrolepidoptera of about 240 species in a light-trap at Harpenden is analysed in relation to Fisher's mathematical theory and is shown to fit extremely closely to the calculations. The calculations are applied first to the frequency of occurrence of species represented by different numbers of individuals--and secondly to the number of species in samples of different sizes from the same population. The parameter ` alpha ', which it is suggested should be called the `index of diversity', is shown to have a regular seasonal change in the case of the Macrolepidoptera in the trap. In addition, samples from two traps which overlooked somewhat different vegetation are shown to have ` alpha ' values which are significantly different. It is shown that, provided the samples are not small, ` alpha ' is the increase in the number of species obtained by increasing the size of a sample by e (2.718). A diagram is given (Fig. 8) from which any one of the values, total number of species, total number of individuals and index of diversity (alpha), can be obtained approximately if the other two are known. The standard error of alpha is also indicated on the same diagram. Part 3. A theoretical distribution is developed which appears to be suitable for the frequencies with which different species occur in a random collection, in the common case in which many species are so rare that their chance of inclusion is small. The relationships of the new distribution with the negative binomial and the Poisson series are established. Numerical processes are exhibited for fitting the series to observations containing given numbers of species and individuals, and for estimating the parameter alpha representing the richness in species of the material sampled; secondly, for calculating the standard error of alpha, and thirdly, for testing whether the series exhibits a significant deviation from the limiting form used. Special tables are presented for facilitating these calculations.
Epiphytes in rain forests of Venezuela -diversity and dynamics of a biocenosis
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