Species Turnover Research Articles

Decline in alien plant species turnover among geographically isolated mountains with ropeway corridors

Anthropogenic corridors facilitate alien invasions from low to high elevations in mountains. While native plant assemblages generally show a large elevational turnover to alpine species, alien plant assemblages at high elevations seem to consist of only generalist species with broad tolerances, resulting in a nested structure of lowlands. These may cause homogeneous alien plant assemblages even in geographically isolated higher elevations, thereby undermining the alpine flora uniqueness. We focused on ropeway corridors that may facilitate alien invasions up long elevational gradients from lowlands, and examined the followings on 14 mountains across Japan: Are alien plant assemblages at high elevations accessible by ropeways formed as a subset of lowland alien species? and Are alien plant assemblages homogeneous among isolated higher elevations? We analyzed species richness and spatial turnover of alien and native species at the lower and upper ends of ropeways, as well as the effects of geographical and climatic factors on the spatial turnover and alien species’ presence probability at upper ends. Alien species richness decreased with elevation, whereas native species richness did not. The degree of spatial turnover of alien species was lower than that of native species, especially at upper ends, and was not affected by coordinal distance, unlike native species. The alien species’ presence probability at the upper ends was influenced by that at the lower ends. Our results highlight that homogeneous alien plant assemblages are formed across isolated higher elevations with ropeways. Strengthening the management of lowland alien species pools is necessary to conserve mountain biodiversity.

Selenium alters the gene content but not the taxonomic composition of the soil microbiome

Abstract Background Microbiomes, essential to ecosystem processes, face strong selective forces that can drive rapid evolutionary adaptation. However, our understanding of evolutionary processes within natural systems remains limited. We investigated evolution in response to naturally occurring selenium in soils of different geological parental materials on the Western Slope of Colorado. Our study focused on examining changes in gene frequencies within microbial communities in response to selenium exposure. Results Despite expectations of taxonomic composition shifts and increased gene content changes at high-selenium sites, we found no significant alterations in microbial diversity or community composition. Surprisingly, we observed a significant increase in differentially abundant genes within high-selenium sites. Conclusions These findings are suggestive that selection within microbiomes primarily drives the accumulation of genes among existing microbial taxa, rather than microbial species turnover, in response to strong stressors like selenium. Our study highlights an unusual system that allows us to examine evolution in response to the same stressor annually in a non-model system, contributing to understanding microbiome evolution beyond model systems.

The Taxonomic and Functional Diversity of Leaf-Litter Dwelling Ants in the Tropical Dry Forest of the Colombian Caribbean

There have been few advances in understanding the organization and dynamics of ants in tropical dry forests. The latter are a seriously threatened ecosystem, and ants are important indicators of diversity, disturbance, and restoration in forest ecosystems. Using diversity data and morphofunctional traits, we evaluated the spatial and temporal variation of taxonomic and functional ant groups; in addition, we explored the variation in functional traits and diversity among communities. Ants were sampled during the dry and rainy seasons using mini-Winkler bags. A total of 9 subfamilies, 57 genera, and 146 species were collected. Ant species composition and richness varied both spatially (75 to 119 species) and temporally (121 and 127 species). The fragments from N2 and N3 showed higher diversity than those from N1. The dissimilarity among all areas was moderate (50–60%), mainly attributable to species turnover processes (77%). Twenty functional groups were identified. The N3 fragments had the highest functional diversity, with lower resistance to species loss, while the N1 and N2 fragments reduced functional diversity and increased similarity among species. Our results highlight the importance of integrating a functional analysis with the taxonomic assessment of ants as an important contribution to understanding the organization and dynamics of this community of insects that inhabit the tropical dry forest.

Reaching new heights: Arboreal ant diversity in a North American temperate forest ecosystem

Abstract Most canopy insect research takes place in tropical forests, where communities are highly vertically stratified. However, temperate forest canopies also provide critical resources to many species and are under intense pressure from global change drivers. The relative lack of knowledge regarding temperate canopy insect ecology impedes our forest management and conservation decisions such that we may be losing temperate canopy biodiversity before we know it exists. We directly compared ant diversity and community composition on the ground and in the tree canopy of North American temperate deciduous forests for the first time. We also evaluated two canopy sampling methods—baits and hand collections. We collected 34 ant species from 102 trees across seven sites. Ant diversity was greater on the ground than in the canopy, and species turnover created distinct communities across vertical strata. Only 12% of species were exclusively arboreal, but 47% were collected in both strata, indicating the canopy is an important resource for temperate ants, even if they are not restricted there. Baiting and hand‐collecting recovered similar species richness, but whether baits captured a subset of hand‐collected species or a unique assemblage was site‐dependent. Nevertheless, we suggest that these methods are most effective in conjunction. Hand collection allowed us to document arboreal nests of 10 species, including the invasive needle ant, Brachyponera chinensis, which was previously thought to be strictly terrestrial. Our results emphasise the importance of including the canopy in temperate forest ecology and conservation assessments.

Settlement patterns and temporal successions of coral reef cryptic communities affect diversity assessments using autonomous reef monitoring structures (ARMS)

Autonomous Reef Monitoring Structures (ARMS) are used worldwide to assess cryptic diversity, especially on coral reefs. They were developed as standardised tools, yet conditions of deployment, such as immersion duration and/or deployment and retrieval seasons, vary among studies. Here we studied temporal and seasonal variability in coral reef cryptic communities sampled with 15 ARMS on a single coral reef slope site at Reunion Island, Southwest Indian Ocean. Settlement patterns and temporal succession of Eukaryote communities were investigated across three immersion times (6 months, 1 year, 2 years), two immersion seasons (hot vs. cool) and three fractions (500–2000 μm, 106–500 μm, sessile) using two genetic markers (18S, COI). Both markers detected different taxa with different resolutions, but broadly similar patterns of community composition and structure. While OTU diversity of communities did not change with immersion time and season, these parameters significantly affected community structure and composition. Our results showed a decrease of the similarity of ARMS communities with duration of immersion, and a strong temporal turnover of species with only a small proportion of the diversity persisting over time. The small proportion of OTUs assigned at phylum level highlights the uniqueness of the Mascarene cryptobiome.

Glacier retreat decreases mutualistic network robustness over spacetime

Glaciers are retreating worldwide at an ever‐increasing rate, exposing new ice‐free areas to ecological succession. This process leads to changes in biodiversity and potentially to novel species interactions. However, we still have a limited understanding of how glacier retreat influences species interaction networks, particularly the structure and robustness of mutualistic networks. After reconstructing plant–pollinator networks along a 140‐years chronosequence on a glacier foreland, we address the effects of glacier retreat on network structure and robustness. Our results show that the prevalence of different network motifs changes over spacetime, leading to a decrease of network robustness. With glacier retreat, mutualistic networks shift from highly connected with diverse specialist interactions to loosely connected with few generalist interactions. Furthermore, despite the turnover of plant species, we find that species structural roles remain constant over spacetime while depending on species identity. Our findings suggest that glacier retreat reshuffles mutualistic networks with motifs posing low robustness, leading to increased fragility. Understanding the assembly and breaking down of species interaction networks provides novel insights into the development and stability of novel, post‐glacial ecological systems facing glacier extinction.

Flying by night: Comparing nocturnal pollinator networks over time in the Colorado Rocky Mountains

Abstract Where climate is seasonal, such as in high‐altitude ecosystems, the occurrence and activity patterns of insect pollinators may vary with the varying occurrence of floral resources. This high turnover of species occurrence and interactions may lead to changes in the structure and properties of plant–pollinator networks. Here, we systematically compared the properties of moth pollen‐transport networks in Colorado, USA, over the course of a season, and tested for a link between moth species specialisation and morphology. We predicted that network properties would change through the season as the abundance and diversity of available floral resources increased. We also predicted that there would be a link between moth specialisation and morphology, as moth proboscis length can restrict their ability to utilise different floral resources. We sampled moths for pollen over 9 weeks in June through August 2021. We then constructed pollen‐transport networks, and used mixed models to test for differences in network indices between different parts of the 2021 season; we also tested for a relationship between moth proboscis length, the duration of moth species' presence across the season and the number of flower species pollinated. As expected, we found high rates of species turnover and high rates of plant–pollinator interactions over the summer. However, linkage density and robustness were the only overall network metrics that changed. We also found that longer proboscis lengths and more persistent species occurrence over the season were predictive of higher generalisation among moth species. We suggest that even with high rates of species turnover, nocturnal moth pollen‐transport networks may maintain their overall structure over a season, with variations in the availability of floral resources driving limited variation in some network metrics. Our study highlights the necessity of continuing to research moth pollen‐transport networks over different temporal scales, to better understand how ecological factors can lead to changes in network structure over time.

Macrofaunal Biodiversity and Patch Mosaics on the Deep Gulf of Mexico Seafloor

ABSTRACTThe deep‐sea benthos often exhibit exceptional biodiversity. The patch‐mosaic hypothesis proposes that this deep‐sea diversity arises from varied microhabitats with prolonged temporal persistence filtering for distinctive communities thereby increasing beta‐diversity. This study investigated environmental, community, and macrofaunal species turnover at four deep‐sea sites (~2000 m) in the northern Gulf of Mexico. Using precise small‐scale sampling with a ROV, we analyzed patterns across spatial scales from centimeters to approximately 400 km among 67 sediment cores. We examined the relationships between sedimentary carbon, sediment grain size, and macrofaunal alpha‐ and beta‐diversity. Subsequently, we explored the role of these environmental properties and their spatial arrangement in shaping communities and species distributions. We observed a consistent trend where the overall abundance and diversity of a community increased with higher carbon but decreased with increasing grain size. Substantial faunal turnover was observed among cores, even at centimeter scales, with the contribution of centimeter‐scale spatial distance rivaling that of 100‐km scales in faunal dissimilarity. Similar to alpha‐diversity, beta‐diversity exhibited strong correlations with sediment carbon and grain size. The observed random spatial structure in grain size and carbon appear to translate into randomness in both community and species distribution. These findings align with the patch‐mosaic model, underscoring the complexity of deep‐sea ecosystems. These findings suggest an intricate relationship between sedimentary attributes, faunal composition, and spatial arrangement in the deep‐sea benthos, shedding light on the mechanisms driving biodiversity in seemingly homogeneous environments.

Lessons from long‐term research: Diptera species turnover and dominance shifts with respect to climate‐driven changes

Abstract The diverse pressures of climate change have influenced many habitats, especially freshwater ones, due to their greater sensitivity to stressors. Aquatic Diptera make up more than 50% off all aquatic insect species described, which makes them an ideal group to monitor changing climate as their diverse assemblages can reflect functions within the entire community. The aim of this research was to identify variations in the aquatic dipteran community during a 15‐year period at a tufa barrier in a karst barrage lake system and to determine the environmental factors that have the highest influence on this community. We analysed monthly data collected between 2007 and 2021, when we collected adult specimens using 6 pyramid‐type emergence traps. In total, 167 taxa from 13 different families were gathered. NMDS based on Bray–Curtis similarity analysis amongst assemblages revealed the segregation of samples based on different current velocities and substrates, indicating the importance of microhabitats in dipteran community structuring. Dipteran taxa indicative of specific 5‐year time periods within the research were identified and were associated with changes in environmental conditions especially discharge. The threshold indicator taxa analysis revealed specific species' responses to changing discharge rates. The study shows that discharge rate, not water temperature, is the critical factor shaping dipteran composition, whether by removing or adding taxa to the community. Species turnover showed an overall decrease in species numbers, that is, species richness, throughout the research period. We conclude that changes in the dipteran community, because of the vast functional traits, niches, adaptations and species diversity of the group, are not visible when analysing just the diversity indices. When determining environmental influence on the community in long‐term research, they should be combined with other data such as the overall abundance, the total number of species, as well as the species turnover.

Caves’ environmental stability shaping subterranean biodiversity in the neotropics

Caves, once thought to be isolated ecosystems", are now understood to have intricate connections with surface environments, particularly evident at their entrances. These connections can significantly affect the microclimate within caves, leading to varying degrees of environmental stability. Our research explores the impact of microclimate conditions, specifically related to cave environmental stability, on biodiversity changes. We surveyed subterranean invertebrates during two different seasonal periods in 17 limestone caves in three karst regions in southeastern Brazil. Our analysis aimed to understand how environmental stability influences the overall richness of cave invertebrates and troglobitic species richness (restricted to subterranean habitats). We hypothesized that more stable caves would experience less fluctuation in relative species richness and lower turnover between seasons. Additionally, we anticipated that caves with greater environmental stability would harbor a higher richness of cave-restricted species in the function of their length. Our findings support these hypotheses, revealing a significant positive correlation between cave environmental stability and species richness. Caves with higher environmental stability demonstrated lower species turnover rates between seasons, indicating enhanced community stability. While environmental stability significantly affected species richness, its influence on cave-restricted species was comparatively less pronounced. This suggests a complex interplay of factors shaping the unique fauna of caves. Nonetheless, the implications of climate change underscore the importance of preserving the environmental stability of these ecosystems. Using environmental stability as a guide can help protect cave biodiversity from the adverse effects of climate change, contributing to broader conservation efforts for these unique habitats.

Effect of environmental DNA sampling resolution in detecting nearshore fish biodiversity compared to capture surveys.

Sampling and sequencing marine environmental DNA (eDNA) provides a tool that can increase our ability to monitor biodiversity, but movement and mixing of eDNA after release from organisms before collection could affect our inference of species distributions. To assess how conditions at differing spatial scales influence the inferred species richness and compositional turnover, we conducted a paired eDNA metabarcoding and capture (beach seining) survey of fishes on the coast of British Columbia. We found more taxa were typically detected using eDNA compared to beach seining. eDNA identified more taxa with alternative habitat preferences, and this richness difference was greater in areas of high seawater movement, suggesting eDNA has a larger spatial grain influenced by water motion. By contrast, we found that eDNA consistently missed low biomass species present in seining surveys. Spatial turnover of communities surveyed using beach seining differed from that of the eDNA and was better explained by factors that vary at small (10-1000s meters) spatial scales. Specifically, vegetation cover and shoreline exposure explained most species turnover from seining, while eDNA turnover was not explained by those factors and showed a distance decay pattern (a change from 10% to 25% similarity from 2 km to 10 km of distance), suggesting unmeasured environmental variation at larger scales drives its turnover. Our findings indicate that the eDNA sample grain is larger than that of capture surveys. Whereas seining can detect differences in fish distributions at scales of 10s-100s of meters, eDNA can best summarize fish biodiversity at larger scales possibly more relevant to regional biodiversity assessments.

A Stroll Along Australian Ecosystems: Using Bioclimatic Transects to Examine Environmental Drivers of Community Assembly in Birds

ABSTRACTAimVariation in community composition along environmental gradients provides crucial information for identifying zones where species turnover is rapid and to ascertain whether compositional changes occur gradually or rather abruptly. We examined changes in bird community composition along three bioclimatic transects in Australia to test whether drivers of species turnover are consistent, rather than spatially contingent, across biologically contrasting ecosystems. We also detected potential transition zones associated with environmental thresholds and determined whether certain abiotic conditions promote a higher rate of community compositional turnover.LocationMainland Australia.TaxonTerrestrial birds.MethodsWe applied multivariate community analysis, generalised dissimilarity modelling (GDM) and threshold indicator taxa analysis (TITAN).ResultsWe observed that environmental variables are better predictors of community composition than spatial distance, which indicates that species sorting, rather than dispersal, plays a key role in structuring Australian avian communities. Annual precipitation constitutes a key driver of species turnover regardless of the analysed transect. The most humid landscapes and those with a higher tree canopy show lower spatial heterogeneity in community composition compared to those with less benign environmental conditions (e.g., dryer environments). TITAN detected significant transition points and supported the results obtained using GDM, which suggests that bird composition change along the gradients is not monotonic.Main ConclusionsOur results suggest that avian beta diversity increases with increasing environmental harshness, presumably through changes in the relative importance of stochastic versus deterministic processes. The obtained findings show that open forests and woodlands are extremely important ecosystems on this continent and deserve special attention in terms of conservation due to their vulnerability to global change. Lastly, this study exemplifies the value of combining community‐ and taxon‐based analyses to identify and interpret community thresholds, which can serve to pinpoint targets for preserving biodiversity.

Plant diversity value of informal green spaces in tropical coastal urban areas: An empirical study of species, functional, and phylogenetic diversity

Informal green spaces (IGS) are a hot topic in urban biodiversity studies, but overlooked in urban biodiversity conservation or management, especially in tropical coastal cities, where comprehensive assessments remain scarce. Most existing research has been limited to species diversity (α-diversity), with few studies addressing functional and phylogenetic diversity as aspects of α-diversity, and species turnover (β-diversity) across multiple IGS types. This study bridges these gap by conducting a detailed vegetation survey in Jiangdong New Area of Haikou City, establishing 213 sites. Within these sites, we examined 343 IGS sample plots and 274 formal green spaces (FGS) sample plots. We assessed species, functional, and phylogenetic diversity using α and β diversity metrics and analyzed the influence of environmental factors with generalized linear mixed models (GLMMs). The results recorded 235 species of herbaceous plants from 179 genera and 54 families in IGS, including 215 spontaneous species, compared to 154 spontaneous species in FGS. Our findings indicate that IGS exhibited higher species richness and functional richness compared to FGS, though differences in phylogenetic diversity were less pronounced. Key environmental factors like relative humidity, trampling intensity, and proximity to urban areas significantly influenced species richness and abundance in IGS. These findings underscore the critical role of IGS in enhancing biodiversity and resilience in tropical coastal cities, emphasizing the need to integrate IGS into urban planning strategies for sustainable urban ecosystems.

Lake Bacterial Communities in North Patagonian Andes: The Effect of the Nothofagus pumilio Treeline

One of the most noticeable environmental discontinuities in mountains is the transition that exists in vegetation below and above the treeline. In the North Patagonian Andean lakes (between 900 and 1950 m a.s.l.), we analyzed the bacterial community composition of lakes in relation to surrounding vegetation (erected trees, krummholz belt, and bare rocks), dissolved organic carbon (DOC), and total dissolved nutrients (nitrogen, TDN and phosphorus, TDP). We observed a decrease in DOC, TDP, and TDN concentrations with altitude, reflecting shifts in the source inputs entering the lakes by runoff. Cluster analysis based on bacterial community composition showed a segregation of the lakes below treeline, from those located above. This first cluster was characterized by the cyanobacteria Cyanobium PCC-6307, while in the krummholz belt and bare rocks, bacterial communities were dominated by Actinobacteria hgcl-clade and Proteobacteria (Sandarakinorhabdus and Rhodovarius), with the presence of pigments such as actinorhodopsin, carotenoids, and bacteriochlorophyll a. The net relatedness index (NRI), which considers the community phylogenetic dispersion, showed that lakes located on bare rocks were structured by environmental filtering, while communities of lakes below treeline were structured by species interactions such as competition. Beta-diversity was higher among lakes below than among lakes located above the treeline. The contribution of species turnover was more important than nestedness. Our study brings light on how bacterial communities may respond to changes in the surrounding vegetation, highlighting the importance of evaluating different aspects of community structure to understand metacommunity organization.

More the merrier? influence of mango orchards on the composition of the reptile communities of the lateritic plateaus, Maharashtra, India

AbstractChange in land‐use patterns affects a landscape by changing the composition of local flora and fauna. The lateritic plateaus in Konkan are one such example of this rapid land‐use change. Although these plateaus are rich in endemic flora and fauna, they are considered as “wastelands” due to lack of woody vegetation and thus, are subjected to various land‐uses. Mango cultivation in this region has become a major source of income due to its Alphonso variety of mangoes. Hence, over the last few decades, many plateaus have been converted into mango orchards. However, how the conversion of plateaus to mango orchards has affected species composition of different groups of organisms remains unclear. In the present study, we sampled the lateritic plateaus and plateaus converted into mango orchards in Ratnagiri, Maharashtra, to investigate the response of the reptile communities. We observed more species heterogeneity in the orchards compared to the unaltered sites. Moreover, it appeared that there was a species turnover when the plateaus were converted into orchards. The generalist and widespread species such as agamids and skinks and very few specialist species were comparatively more abundant in the orchards. On the contrary, the plateaus without orchards harbored more specialist species such as Hemidactylus albofasciatus (n = 62, in unaltered sites vs. n = 5 in the orchards), Echis carinatus (n = 15 in unaltered sites and none in the orchards) and Ophisops jerdonii (n = 45 in unaltered site vs. n = 12 in the orchards) compared to the generalist species.

Influence of climate, weather and floral associations on pollinator community composition across an elevational gradient

Insect pollinators, which are ectothermic, are especially sensitive to abiotic conditions, which often drive predictable patterns of pollinator species turnover along environmental gradients. However, pollinator activity is also reliant on suitable biotic conditions, such as the presence of host plants. High‐elevation environments provide a useful setting to examine the relative contribution of abiotic and biotic factors in shaping species interactions as they are often characterised by strong environmental gradients over short geographic distances. Here, we examined pollination interaction networks across an elevational gradient from 930–2000 m a.s.l. in southern Australia, to determine the underlying patterns of pollinator activity and their interactions with flowers. Interaction frequency of Diptera increased at high elevations, while interaction frequency of Hymenoptera and Coleoptera decreased. We provide evidence that this elevational pattern of activity is partly driven by floral associations, with interactions dominated by Hymenoptera‐attracting plant families at lower elevations (Proteaceae, Fabaceae) and a Diptera‐attracting family at high elevation (Asteraceae). Pollinator activity was also influenced by weather conditions, with reduced activity for all three orders at lower temperatures, and Diptera active across the broadest range of temperature, humidity and wind conditions. We suggest that changes across elevation gradients in pollinator community composition are driven by both direct responses to abiotic conditions such as temperature, as well as the elevational distribution patterns of associated flowering plants. Despite these distinct shifts in composition of the pollinator assemblage with elevation, pollination network structure was stable across the elevational gradient, with moderate levels of specialisation and low levels of connectance and nestedness present across the gradient. By considering both abiotic conditions and biotic processes, our results provide insight for predicting the impacts of upslope vegetation shifts on pollinator communities in the face of climate change.

Slower but deeper community change: Intrinsic dynamics regulate anthropogenic impacts on species temporal turnover.

Understanding the mechanisms behind biodiversity dynamics is central to assessing and forecasting anthropogenic impacts on ecological communities. However, the manner in which external environmental drivers act in concert with intrinsic ecological processes to influence local temporal turnover is currently largely unexplored. Here, we determine how human impacts affect multiple metrics of bird community turnover to establish the ecological mechanisms behind compositional change. We used US Breeding Bird Survey data to calculate transect-level rates of three measures of temporal species turnover: (1) "short-term" (initial rate of decline of Sørensen similarity), (2) "long-term" (asymptotic Sørensen similarity), and (3) "throughput" (overall species accumulation rate from species-time relationship exponents) over 2692 transects across 27 regional habitat types. We then hierarchically fit linear models to estimate the effect of anthropogenic impact on these turnover metrics, using the Human Modification Index proxy, while accounting for observed species richness, the size of the species pool, and annual environmental variability. We found broadly consistent impacts of increased anthropogenic pressures across diverse habitat types. The Human Modification Index was associated with greater turnover at long timescales, but marginally slower short-term turnover. The species "throughput" (accumulation rate) was not notably influenced. Examining anthropogenic impacts on different aspects of species turnover in combination allows greater ecological insight. Observed human impacts on short-term turnover were the opposite of existing expectations and suggest humans are disrupting the background turnover of these systems, rather than simply driving rapid directed turnover. The increased long-term turnover without concurrent increases in species accumulation implies human impacts lead to shifts in species occurrence frequency rather than simply greater arrival of "new" species. These results highlight the role of intrinsic dynamics and caution against simple interpretations of increased species turnover as reflections of environmental change.

The biogeography of the Amazonian tree flora

We describe the geographical variation in tree species composition across Amazonian forests and show how environmental conditions are associated with species turnover. Our analyses are based on 2023 forest inventory plots (1 ha) that provide abundance data for a total of 5188 tree species. Within-plot species composition reflected both local environmental conditions (especially soil nutrients and hydrology) and geographical regions. A broader-scale view of species turnover was obtained by interpolating the relative tree species abundances over Amazonia into 47,441 0.1-degree grid cells. Two main dimensions of spatial change in tree species composition were identified. The first was a gradient between western Amazonia at the Andean forelands (with young geology and relatively nutrient-rich soils) and central–eastern Amazonia associated with the Guiana and Brazilian Shields (with more ancient geology and poor soils). The second gradient was between the wet forests of the northwest and the drier forests in southern Amazonia. Isolines linking cells of similar composition crossed major Amazonian rivers, suggesting that tree species distributions are not limited by rivers. Even though some areas of relatively sharp species turnover were identified, mostly the tree species composition changed gradually over large extents, which does not support delimiting clear discrete biogeographic regions within Amazonia.

Small-scale geographic factors promote a high diversity of amphibians and reptiles in Colombia

Analysing spatial biodiversity patterns in amphibians and reptiles is key to understanding the main drivers of community ecological structure, biogeography, and guiding conservation strategies. Our goal is to map patterns of taxonomic change and unravel the geographic and environmental factors driving species turnover among the biomes found in the Sogamoso river basin (SRB), which tributes to the inter-Andean middle Magdalena valley in Colombia, a hyperdiverse region at high-risk from human activities. The study area encompasses lowland forest, submontane, montane and high-elevation Andean habitats, with distinct biomes defined by elevation and physiographic characteristics. To do this, we compared species richness among different biomes and describe their variation along the altitudinal gradient. We collected data from literature and revision of specimens deposited in herpetological collections. Species distribution models were used to estimate geographic ranges and species composition was analysed among biomes using a presence/absence matrix. Generalised Dissimilarity Modelling (GDM) was employed to explore spatial turnover patterns of species composition. We observed that species richness of both amphibians and reptiles was the highest in the tropical humid forest biome and the lowest occurred mainly in the Sub-Andean semiarid vegetation. The spatial pattern of species turnover was the same for amphibians and reptiles and revealed an extreme similarity with the previous delimitation of the five biomes, which are supported by a combination of biotic, abiotic and anthropogenic factors. This study provides valuable baseline information for the conservation of amphibians and reptiles in the SRB and highlights the importance of considering geographic and environmental factors in understanding species distribution and turnover in the region. Keywords: Sogamoso River, herpetofauna, richness patterns, turnover species, ecological structure

Elevational and Seasonal Patterns of Plant-Hummingbird Interactions in a High Tropical Mountain.

Tropical mountain ecosystems harbor diverse biological communities, making them valuable models for exploring the factors that shape ecological interactions along environmental gradients. We investigated the spatial and temporal drivers of plant-hummingbird interaction networks across three forest types (pine-oak, fir, and subalpine) along a tropical high mountain gradient in western Mexico (2400 to 3700 m.a.s.l.). We measured species abundance, diversity, morphology, and interaction frequencies. Plant diversity metrics significantly declined in the highest elevation subalpine forest, whereas hummingbird diversity remained consistent across elevations. Interaction networks were similarly nested across elevations, but they were more specialized in the subalpine forest, where lower plant species richness and higher floral abundance led to greater resource partitioning among hummingbirds. Plant-hummingbird networks were larger and less specialized during the dry season, driven by greater species diversity and abundance. Species turnover explained network variation along the elevational gradient, while interaction rewiring and the arrival of migratory hummingbirds explained changes between seasons. Phenological overlap was the most important driver of the observed variation in interaction frequencies across elevations and seasons. Flower abundance had a minor influence on interaction frequencies at low- and mid-elevation networks, and hummingbird abundance was significant for dry- and rainy-season networks. Morphological matching was significant in the low-elevation forest and in the dry season. Plant phylogenetic relatedness had negligible effects on interaction patterns, but hummingbird phylogeny influenced feeding preferences in high-elevation and rainy-season networks. Our findings highlight the role of species turnover, interaction rewiring, and phenological overlap in structuring plant-hummingbird networks, with specific effects of abundance, morphology, and phylogeny varying with elevation and season. High-elevation ecosystems play a crucial role as reservoirs of floral resources for both resident and migratory hummingbirds during resource-scarce periods, emphasizing their importance in maintaining biodiversity in tropical mountain gradients.