Regional Richness Research Articles

Naturalized and invasive alien flora of Ghana

The paper provides an inventory of the naturalized vascular flora of Ghana, based on newly gathered information from the literature and consultations with local experts. We adopted a rather conservative approach by including only species for which strong evidence exists that they are alien in Ghana. We recorded 291 species of naturalized alien plants; for 237 of them there is information on their distribution in the 10 administrative regions of Ghana. Twenty-five species (i.e. 8.6% of the total number of naturalized species) are classified as invasive. There are 21 widely distributed species (7.2% of the total naturalized flora) that occur in at least eight regions, and five of them are distributed all over the country: Azadirachta indica, Echinochloa colona, Leucaena leucocephala, Senna occidentalis and S. siamea. Of these five, the first three are classified as invasive. The naturalized flora of Ghana includes 71 families, with Leguminosae (66 species), Compositae (22) and Poaceae (18) most represented. The majority of species have their native range in South and North America, contributing 161 and 127 species, respectively. Tropical Asia (98 species) and Africa (37 species) are less represented and only three species have their origin in Europe. The dominance of the Americas as a source region is even more pronounced for the subset of invasive species, with this continent accounting for 18 species out of 25 (72%). Annual and biennial/perennial herbs, shrubs and trees are evenly represented in the naturalized alien species pool. Among invasive species, biennial/perennial herbs are markedly over-represented compared to their contribution to the naturalized flora as a whole (52% vs 38%). The same is true for aquatic species (12% vs 2%). Species that occur as naturalized in more than 40 regions in Africa are also more widely distributed within Ghana. The numbers of naturalized species in the administrative regions of Ghana varied from 34 in Upper West to 173 in Greater Accra. These numbers increased with human population density and decreased with distance from the sea, but this pattern was driven by the city of Accra region. The only predictor that remained significant after removing this outlier was the amount of precipitation in the dry period, which was positively associated with the regional richness of naturalized species. This study could serve as a stimulus for other countries in hitherto understudied tropical regions to work towards comprehensive inventories, for which basic data on the alien flora often is still incomplete.

Explaining the ocean's richest biodiversity hotspot and global patterns of fish diversity.

For most marine organisms, species richness peaks in the Central Indo-Pacific region and declines longitudinally, a striking pattern that remains poorly understood. Here, we used phylogenetic approaches to address the causes of richness patterns among global marine regions, comparing the relative importance of colonization time, number of colonization events, and diversification rates (speciation minus extinction). We estimated regional richness using distributional data for almost all percomorph fishes (17 435 species total, including approximately 72% of all marine fishes and approximately 33% of all freshwater fishes). The high diversity of the Central Indo-Pacific was explained by its colonization by many lineages 5.3-34 million years ago. These relatively old colonizations allowed more time for richness to build up through in situ diversification compared to other warm-marine regions. Surprisingly, diversification rates were decoupled from marine richness patterns, with clades in low-richness cold-marine habitats having the highest rates. Unlike marine richness, freshwater diversity was largely derived from a few ancient colonizations, coupled with high diversification rates. Our results are congruent with the geological history of the marine tropics, and thus may apply to many other organisms. Beyond marine biogeography, we add to the growing number of cases where colonization and time-for-speciation explain large-scale richness patterns instead of diversification rates.

Are Boreal Riparian Bird Communities Unique? Contrasting Riparian and Upland Bird Assemblages in the Boreal Plain of Western Canada

Riparian ecotones in arid regions often contain unique species and have higher species richness and abundance relative to upland habitats making them of higher conservation priority than other habitats. However, such differences in species richness and abundance may not be apparent in more mesic regions. We compared species frequency of occurrence and abundance, richness and turnover of bird assemblages in two aquatic ecotone types with those in nearby interior upland forests in the boreal forest of Alberta, Canada. Riparian edge habitats had higher species richness and more species with significant indicator values than lowland forest edge or interior upland forest and the greatest differences in bird community composition were between riparian edge and upland interio habitats. Species turnover was highest in riparian habitats attributable to the presence of rare species or higher spatial and structural heterogeneity of those systems. When contrasting the upland forested area adjacent to the waterbody versus a similar sized area in the upland forest interior, riparian areas still contained higher richness but had fewer indicator species. We suggest that riparian areas and the adjacent shoreline forest contribute considerably to the regional richness of bird communities in the boreal forest and management policies should reflect this characteristic.

SPATIAL VARIATION IN BAT SPECIES RICHNESS IN A FOREST-GRASSLAND TRANSITIONAL REGION OF SOUTHEASTERN SOUTH AMERICA

The latitudinal diversity gradient is the most well-known ecological pattern. Several hypotheses have been proposed to explain this biodiversity gradient. However, the predictors of species richness at continental scales may have different effects at regional scales, and even lose importance. Here we tested the effects of climate, energy, and habitat heterogeneity on the spatial variation of bat species richness in a forest-grassland transitional region, in southeastern South America. Our main goals were to assess which variables better explain bat species richness, and to analyze redundancy and complementarity among hypotheses. We generated three regression models, being each model related to a hypothesis, and compared R-squared among models. Then, we estimated redundancy and complementarity among hypotheses by partitioning the variation in species richness into unique and shared effects among hypotheses. Climate explained a larger proportion of the spatial variation of bat species (R² = 0.97, p < 0.0001), followed by heterogeneity (R² = 0.94, p < 0.0001), and energy (R² = 0.93, p < 0.0001), respectively. Variation partitioning analysis showed that climate explained the largest proportion of richness variation (83%). Energy and heterogeneity explained 55% and 51% of bat richness, respectively. The amount of variation explained uniquely by climate and heterogeneity were identical (R² = 0.09) whereas energy explained a small fraction of the variation (R² < 0.01). We conclude that climatic conditions coupled with habitat heterogeneity were the main predictors of bat richness in a forest-grassland transitional region and that the variables explaining regional richness gradient were the same at continental scale.

Species turnover drives β-diversity patterns across multiple spatial scales of plant-galling interactions in mountaintop grasslands.

This study describes differences in species richness and composition of the assemblages of galling insects and their host plants at different spatial scales. Sampling was conducted along altitudinal gradients composed of campos rupestres and campos de altitude of two mountain complexes in southeastern Brazil: Espinhaço Range and Mantiqueira Range. The following hypotheses were tested: i) local and regional richness of host plants and galling insects are positively correlated; ii) beta diversity is the most important component of regional diversity of host plants and galling insects; and iii) Turnover is the main mechanism driving beta diversity of both host plants and galling insects. Local richness of galling insects and host plants increased with increasing regional richness of species, suggesting a pattern of unsaturated communities. The additive partition of regional richness (γ) into local and beta components shows that local richnesses (α) of species of galling insects and host plants are low relative to regional richness; the beta (β) component incorporates most of the regional richness. The multi-scale analysis of additive partitioning showed similar patterns for galling insects and host plants with the local component (α) incorporated a small part of regional richness. Beta diversity of galling insects and host plants were mainly the result of turnover, with little contribution from nesting. Although the species composition of galling insects and host plant species varied among sample sites, mountains and even mountain ranges, local richness remained relatively low. In this way, the addition of local habitats with different landscapes substantially affects regional richness. Each mountain contributes fundamentally to the composition of regional diversity of galling insects and host plants, and so the design of future conservation strategies should incorporate multiple scales.

What explains high plant richness in East Asia? Time and diversification in the tribe Lysimachieae (Primulaceae)

What causes the disparity in biodiversity among regions is a fundamental question in biogeography, ecology, and evolutionary biology. Evolutionary and biogeographic processes (speciation, extinction, dispersal) directly determine species richness patterns, and can be studied using integrative phylogenetic approaches. However, the strikingly high richness of East Asia relative to other Northern Hemisphere regions remains poorly understood from this perspective. Here, for the first time, we test two general hypotheses (older colonization time, faster diversification rate) to explain this pattern, using the plant tribe Lysimachieae (Primulaceae) as a model system. We generated a new time-calibrated phylogeny for Lysimachieae (13 genes, 126 species), to estimate colonization times and diversification rates for each region and to test the relative importance of these two factors for explaining regional richness patterns. We find that neither time nor diversification rates alone explain richness patterns among regions in Lysimachieae. Instead, a new index that combines both factors explains global richness patterns in the group and their high East Asian biodiversity. Based on our results from Lysimachieae, we suggest that the high richness of plants in East Asia may be explained by a combination of older colonization times and faster diversification rates in this region.

Scale sensitivity of the relationship between alpha and gamma diversity along an alpine elevation gradient in central Nepal

AbstractAimComponents of scale, such as grain, focus and extent, influence the spatial patterns of alpha and gamma diversity and the relationships between them. We explored these scale relations by testing whether the gamma diversity and alpha diversity along an elevation gradient were related independent of scale and whether the elevational patterns of herbaceous and woody species richness were dependent on scale.LocationLangtang National Park, Nepal.MethodsWe estimated alpha diversity (plot richness) for woody and herbaceous plant species along an alpine elevation gradient (3,900–5,000 m a.s.l.) in nested plots of 1 m2, 16 m2 and 100 m2 and gamma diversity (regional richness) from published sources. Generalized linear modelling was used to analyse alpha and gamma diversity and their correspondence at different grain sizes.ResultsElevational trends of gamma and alpha diversity were significantly correlated for both woody and herbaceous species at all grain sizes. The concordance increased with increasing grain size and area for gamma diversity estimation, particularly for the monotonously decreasing elevational gamma and alpha diversity patterns of woody species. The hump‐shaped patterns of elevational gamma and alpha diversity for herbaceous species were also significantly correlated, but the concordance between the alpha diversity of herbaceous species and local gamma diversity was stronger. Elevational patterns of alpha diversity were coarsely consistent across grain sizes, although the patterns became more pronounced at larger grain sizes.Main conclusionsThe correspondence of elevational gamma and alpha diversity was largely scale invariant, implying that elevational and possibly other geographical diversity patterns can reliably be studied at different spatial scales. Nonetheless, the alpha diversity pattern was the least pronounced at fine grain size, particularly for woody life‐forms. This finding suggests that for large‐scale patterns such as elevational gradients at regional or continental scales, coarse grain sizes and large areas for gamma estimation are more appropriate.

Bird Diversity Patterns in the Nuclear Central American Highlands: A Conservation Priority in the Northern Neotropics

The Nuclear Central American Highlands (NCAH) is a mountainous region located within a complex transition zone. Here, we analyzed the distribution patterns of 282 species of resident land birds of the NCAH. We gathered a database with records of presence of species, from which we generated realized ecological niche models using the Genetic Algorithm for Rule Set Production. These ecological niche models were used to obtain maps of each species’ potential distribution and generated species richness maps that were also compared to the map of protected areas. In addition, the maps were overlaid with a 0.25° diameter hexagonal grid to generate a presence–absence matrix to create regionalizations through (a) a Parsimony Analysis of Endemism and (b) a phenogram. Results show contrasting patterns of distribution between total species richness and endemic species richness. The regionalizations show groups influenced by slope and altitude. Species composition is mainly Mesoamerican and Neotropical species. Our results offer a new view of the regional understanding of bird diversity patterns and biogeographical processes that have shaped regional richness, like the effects of the Great American Biotic Interchange that are visible in the species composition of the NCAH. We believe that these maps of both species richness and regionalization can serve as useful tools for conservation biologists and authorities in implementing strategies for the protection of natural areas in the NCAH.

Protecting biodiversity in urbanizing regions: The role of urban reserves for the conservation of Brazilian Atlantic Forest birds

Although the Brazilian Atlantic Forest and other global biodiversity hotspots are rapidly urbanizing, there is little information on the potential of metropolitan regions to safeguard biodiversity within their reserves. We sampled bird assemblages in nine protected areas (14.8–1058ha) of the metropolitan region of João Pessoa, Northeast Brazil, to test the hypothesis that larger urban reserves are more effective than smaller ones in protecting the regional species richness, as more habitat and environmental heterogeneity are available for birds. We recorded 126 species belonging to 41 families, including seven endemics and two introduced species. Thraupidae and Tyrannidae were the most representative families with 16 species each. Larger areas clearly protected greater proportion of the regional species richness, but the smaller areas accounted for at least 35.7% of the regional richness. Differences in size and isolation significantly influenced species similarity, but hunting, catching for illegal trade, presence of exotic predators and noise pollution were likely to affect composition as well. The remarkable bird diversity suggests good potential for legal-based, well-planned birdwatching activities in the studied region. The results highlight that urban reserves of any size are valuable for bird conservation in metropolitan regions, though larger ones should be prioritized.

From patches to richness: assessing the potential impact of landscape transformation on biodiversity

AbstractNatural patchiness and human fragmentation result in habitats that are not continuously distributed. How spatial configuration of patches in fragmented habitats influences biodiversity remains largely controversial. Here, we propose a framework to extend the species–area relationship (SAR) approach to analyze how changes in habitat configuration affect species richness in fragmented habitats. We use hypothetical communities that are characterized by (1) their tolerance to human activities, (2) the dispersal capability of the individuals of any species, (3) the SAR, and (4) the species turnover among patches. Further, the species turnover is a function of (4a) the predictability of species survival and (4b) the species recolonization odds. In our framework, we identify three extreme communities that encompass the richness of all potential different communities, and thus encapsulate the richness of real communities. We propose a graph to visualize the effect of different patch sizes on species richness, an index to quantify those changes, and a second graph using the index to visualize the effect of distance between patches on species richness. After applying our framework and tools to the Tropical Andes, we found strong differences in the impact of natural vs. human‐driven fragmentation on richness between biomes. When projecting future richness values under climate change scenarios, the largest sources of uncertainty in our richness calculation (&gt;90%) were species turnover among patches and species dispersal for most of the biomes rather than future climate or species tolerance to human activities. Habitat loss consistently decreased the species richness; however, fragmentation per se often increased it. The increment was mostly linked to the species turnover rate among patches. Our framework is a new theoretical tool to study the main patterns that underlie regional richness and therefore can provide new insights to face spatial habitat reconfiguration caused by human activities.

Species Richness (of Insects) Drives the Use of Acoustic Space in the Tropics

Acoustic ecology, or ecoacoustics, is a growing field that uses sound as a tool to evaluate animal communities. In this manuscript, we evaluate recordings from eight tropical forest sites that vary in species richness, from a relatively low diversity Caribbean forest to a megadiverse Amazonian forest, with the goal of understanding the relationship between acoustic space use (ASU) and species diversity across different taxonomic groups. For each site, we determined the acoustic morphospecies richness and composition of the biophony, and we used a global biodiversity dataset to estimate the regional richness of birds. Here, we demonstrate how detailed information on activity patterns of the acoustic community (&lt;22 kHz) can easily be visualized and ASU determined by aggregating recordings collected over relatively short periods (4–13 days). We show a strong positive relationship between ASU and regional and acoustic morphospecies richness. Premontane forest sites had the highest ASU and the highest species richness, while dry forest and montane sites had lower ASU and lower species richness. Furthermore, we show that insect richness was the best predictor of variation in total ASU, and that insect richness was proportionally greater at high-diversity sites. In addition, insects used a broad range of frequencies, including high frequencies (&gt;8000 Hz), which contributed to greater ASU. This novel approach for analyzing the presence and acoustic activity of multiple taxonomic groups contributes to our understanding of ecological community dynamics and provides a useful tool for monitoring species in the context of restoration ecology, climate change and conservation biology.

Galling Insects of the Brazilian Páramos: Species Richness and Composition Along High-Altitude Grasslands

In this work, we investigated the factors that determine the distribution of galling insects in high-altitude grasslands, locally called 'campos de altitude' of Mantiqueira Range and tested whether 1) richness of galling insects decreases with altitude, 2) galling insect richness increases with plant richness, 3) variation in galling insect diversity is predominantly a consequence of its β component, and 4) turnover is the main mechanism driving the beta diversity of both galling insects and plants. Galling insect richness did not exhibit a negative relationship with altitude, but it did increase with plant richness. The additive partition of regional richness (γ) into its local and beta components showed that local diversity (α) of galling insects and plants was relatively low in relation to regional diversity; the β component incorporated most of the regional diversity. This pattern was also found in the multiscale analysis of the additive partition for galling insects and plants. The beta diversity of galling insects and plants was driven predominantly by the process of turnover and minimally by nesting. The results reported here point out that the spatial distribution of galling insects is best explained by historical factors, such as the distribution of genera and species of key host plants, as well as their relation to habitat, than ecological effects such as hygrothermal stress - here represented by altitude.

Key environmental determinants of global and regional richness and endemism patterns for a wild bee subfamily

Reports of world-wide decline of pollinators, and of bees in particular, raise increasing concerns about maintenance of pollination interactions. While local factors of bee decline are relatively well known and potential mitigation strategies at the landscape scale have been outlined, the regional and continental-scale threats to bee diversity have only been marginally explored. Here we document large-scale spatial patterns for a representative bee subfamily, the determinants of its species richness, and assess major threats to these pollinators. Using a comprehensive global dataset of Colletinae (genera Colletes, also called “polyester” or “cellophane” bees for their underground nests lined with a polyester secretion, and Mourecotelles), a species-rich subfamily whose organismal and physiological ecology is representative of many bees, we measured species richness and endemism on global to continental scales. We explored the relationships between bee species richness and potential environmental stress factors grouped into three categories: contemporary climate, habitat heterogeneity, and anthropogenic pressure. Bees of the subfamily Colletinae demonstrate the reversed latitudinal gradient in species richness and endemism suggested for bees; the highest species richness of Colletinae was found between 30° and 50° latitude in both the northern and southern hemispheres. Centres of endemism largely overlapped with those of species richness. The importance of the Greater Cape Floristic Region, previously identified as a centre of richness and endemism of bees, was confirmed for Colletinae. On the global scale, present-day climate was a significant predictor of species richness as was flowering plant diversity represented by vascular plant species richness and centres of plant diversity. Our main conclusion is that climate change constitutes a potential threat to bee diversity, as does declining diversity of vascular plants. However, a significant overlap between centres of bee richness and plant diversity might increase chances for developing conservation strategies.

Disentangling the influence of environmental and anthropogenic factors on the distribution of endemic vascular plants in Sardinia.

Due to the impelling urgency of plant conservation and the increasing availability of high resolution spatially interpolated (e.g. climate variables) and categorical data (e.g. land cover and vegetation type), many recent studies have examined relationships among plant species distributions and a diversified set of explanatory factors; nevertheless, global and regional patterns of endemic plant richness remain in many cases unexplained. One such pattern is the 294 endemic vascular plant taxa recorded on a 1 km resolution grid on the environmentally heterogeneous island of Sardinia. Sixteen predictors, including topographic, geological, climatic and anthropogenic factors, were used to model local (number of taxa inside each 1 km grid cell) Endemic Vascular Plant Richness (EVPR). Generalized Linear Models were used to evaluate how each factor affected the distribution of local EVPR. Significant relationships with local EVPR and topographic, geological, climatic and anthropogenic factors were found. In particular, elevation explained the larger fraction of variation in endemic richness but other environmental factors (e.g. precipitation seasonality and slope) and human-related factors (e.g. the Human Influence Index (HII) and the proportion of anthropogenic land uses) were, respectively, positively and negatively correlated with local EVPR. Regional EVPR (number of endemic taxa inside each 100 m elevation interval) was also measured to compare local and regional EVPR patterns along the elevation gradient. In contrast to local, regional EVPR tended to decrease with altitude partly due to the decreasing area covered along altitude. The contrasting results between local and regional patterns suggest that local richness increases as a result of increased interspecific aggregation along altitude, whereas regional richness may depend on the interaction between area and altitude. This suggests that the shape and magnitude of the species-area relationship might vary with elevation. This work provides—for the first time in Sardinia—a comprehensive analysis of the influence of environmental factors on the pattern of EVPR in the entire territory, from sea level to the highest peaks. Elevation, as well as other environmental and human-related variables, were confirmed to be influencing factors. In addition, variations of EVPR patterns at regional-to-local spatial scales inspire next investigations on the possible interaction between elevation and area in explaining patterns of plant species richness.

Estimating regional species richness: The case of China's vascular plant species

AbstractAimThe estimation of regional species richness has been a major challenge in ecology but is crucial for setting up conservation priorities. Discovery curves are a principal tool for estimating regional richness, but they have been criticized for being too sensitive to historical fluctuations in species discovery. In this study we propose a new discovery model that considers historical influences. We have applied the model to estimate the number of vascular plant species in China, a country of mega‐biodiversity that has also suffered endless wars and social turmoil in its modern history.LocationChina.Time period1755–2000.Major taxa studiedVascular plant species.MethodsWe compiled the discovery time for each vascular species from the complete volumes of Flora of China, leading to 31,220 valid species names. We applied our model to these data and compared the performance of our model with existing discovery models and two other methods (species–area relationships and a taxonomic rank curve model). We also tested our model with three other independent datasets and one simulation study.ResultsOur new method estimated there to be 36,554 (± 2,708) vascular plant species in China. Our model accounted very well for the effect of historical events and was robust to different periods of data that were used to estimate the total richness. Our model outperformed all other models that were compared. We found that 5,334 species remained to be discovered in China and it would take about 50 years to discover all the species should the current discovery rate of 110 species per year persist.Main conclusionsSpecies discovery curves, with historical effects being properly accounted for, offer a promising tool for estimating regional species richness. Our model is robust to the effect of historical events and provides by far the most accurate and reliable estimates of species richness of test data, including vascular plant richness in China.

Using regional patterns for predicting local temporal change: a test by natural experiment in the Great Lakes bioregion, Ontario, Canada

AbstractAimIt has been found that species richness can be a peaked function of natural area, meaning that conversion of natural cover can increase species numbers. Here, we test whether regional richness–environment relationships can predict local change in species richness.LocationThe greater park ecosystem of Thousand Islands National Park (TINP ecosystem), Ontario, Canada.MethodsWe evaluated change in bird richness in 85 100‐km2 sites, censused from 1981 to 1985 and from 2001 to 2005. We related change in richness over 20 years to change in natural land cover for sites having initially less or greater than half natural area to determine whether richness changes in the direction predicted. We also assessed the extent to which local effects (site‐level extinction and colonization based on species‐specific habitat amount and neighbourhood occupancy by conspecifics) affected the predictability of species richness response to environmental change.ResultsLocal effects predicted bird richness changes through time far better than natural area change (adjusted r2 = 0.56 vs. adjusted r2 = 0.13). Species richness did not consistently respond to change in natural area in the directions predicted by the broader spatial richness–environment relationship, tending to increase with decrease in natural area regardless of the initial amount of natural area. The observed natural area changes (+0.7 km2 to −4.4 km2) were small relative to the changes in richness (+60 species to −37 species), likely impacting our ability to detect a response.Main conclusionsThe importance of local effects observed here in determining site‐level species presence and consequently species richness has implications for species monitoring and the use of species richness as a measure of the avian response to land cover modification in Ontario. Detecting richness responses to environmental changes may often be challenged by low ‘signal‐to‐noise’ ratios and highlights the benefits of long‐term species monitoring.

Geographical variation in the contribution of planted and natural pine forests to the conservation of bird diversity

AbstractAimTree plantations can have beneficial or detrimental effects on regional biodiversity. Here, we focus on how the contribution of pine plantations to the maintenance of regional bird diversity varies geographically compared to natural pine forests, after controlling for the effects of other factors that are known to influence the regional richness of pine forest dwelling birds.LocationSpain.MethodsWe combined large‐scale datasets from diverse sources (i.e. the Spanish Breeding Bird Atlas, the Third Spanish Forest Inventory, land use and forest distribution maps) to analyse the geographical variation of the contribution of pine plantations in relation to their natural counterparts to the maintenance of the regional species richness of pine forest dwelling birds. To do so, we also controlled for the main environmental, land use and forest structure factors using GLM models.ResultsDifferences in bird diversity among planted and natural pine forests varied along latitudinal and longitudinal gradients after accounting for altitude, climate, land uses and vegetation structure of pine forests. Planted pine forests in the north‐west of the Iberian Peninsula have the lowest bird species richness as compared to natural pine forests, and that difference decreased following a north‐west–south‐east gradient. Differences also varied among pine species; they were larger for the species with a higher productive vocation (Pinus sylvestris, Pinus nigra and Pinus pinaster) and not significantly different from zero for species with low commercial interest and mainly used for the restoration of tree cover (i.e. Pinus halepensis).Main conclusionsThe potential of plantations or natural pine forests to enhance biodiversity is highly dependent on both the pine species and the geographical location. On this basis, we identify the geographical areas (and pine species) where a major naturalization effort of plantations would be needed to increase bird diversity.

Factors affecting regional diversity and distribution of freshwater microcrustaceans (Cladocera, Copepoda) at high latitudes

Microcrustaceans (MCs) are an important component of freshwater ecosystems, and their local diversity is known to be driven by many factors. What are the relative contributions of these factors at the larger geographic scale? We analyzed the faunal richness and composition of freshwater Cladocera and Copepoda from 27 mainland and insular circumpolar regions (46°–85°N) to determine the main patterns of their species richness and distribution. The average warmest month air temperature was the primary factor affecting MC richness. Regional richness decreased sharply when the temperature dropped below 12–13 °C, and this effect was more pronounced for Cladocera. As a result, the Cladocera/Copepoda species ratio increased significantly with temperature. The total MC richness and cladoceran richness increased with the ice-free area of a region, while the copepod richness decreased on islands with increasing distance from the mainland. Copepod richness was lower in regions that were glaciated during the Quaternary period. Faunal composition significantly differed between cold and warm regions, as well as between the Palearctic and Nearctic, whereas it was affected by neither the glaciation history nor insularity. The contemporary climate had a stronger effect on the cladoceran distribution, whereas the copepods’ ranges were often restricted to a single continent. The former parts of the intercontinental land bridges are primarily inhabited by Holarctic or cosmopolitan species, with almost equal Nearctic and Palearctic components, which indicates repeated colonization events of these regions from various sources. These findings suggest a key role of contemporary climate (especially for cladocerans) and dispersal limitations (primarily for copepods) in structuring MC faunas at high latitudes, and they may help assess possible changes due to global warming.

Surface water connectivity drives richness and composition of Arctic lake fish assemblages

Summary Surface water connectivity can influence the richness and composition of fish assemblages, particularly in harsh environments where colonisation factors and access to seasonal refugia are required for species persistence. Studies regarding influence of connectivity on Arctic fish distributions are limited and are rarely applied to whole assemblage patterns. To increase our understanding of how surface water connectivity and related hydrologic variables influence assemblage patterns, we investigated species richness and composition of Arctic lake fishes over a large region, 8500 km2, of the central Arctic Coastal Plain, Alaska. We collected fish presence/non‐detection data from 102 lakes and used a hierarchical multispecies occupancy framework to derive species richness and inform species composition patterns. Our mean estimate of regional richness was 12.3 (SD 0.5) species. Presence of a permanent channel connection was an overriding factor affecting species richness (mean 3.6, 95% CI 3.1–4.9), presumably driving lake colonisation potential. In lakes without a permanent channel connection, data suggest richness (mean 2.0, 95% CI 1.7–3.3) increased with the availability of in‐lake winter refugia and with the potential of ephemeral connections during spring floods. Fish species functional traits and environmental faunal filters contributed to patterns of richness and assemblage composition. Composition corresponded with richness in a coherent manner, where each successive level of richness contained several discrete assemblages that showed similar responses to the environment. Lakes with permanent channel connections contained both widespread and restricted species, while the species‐poor lakes that lacked a connection contained mainly widespread species. This work provides useful baseline information on the processes that drive the relations between patch connectivity and fish species richness and assemblage composition. The environmental processes that organise fish assemblages in Arctic lakes are likely to change in a warming climate.

The geography of speciation in coral reef fishes: the relative importance of biogeographical barriers in separating sister‐species

AbstractAimTo understand how geography has influenced the generation and maintenance of biodiversity. We examined the relative importance of biogeographical barriers in the divergence of extant coral reef fish species.LocationPan‐tropical coral reefs.MethodsSister‐species were identified from a recent phylogeny encompassing four fish families (Chaetodontidae, Epinephelidae, Labridae and Pomacanthidae) and classified as allopatric or overlapping based on data compiled from IUCN maps. Nearest linear distances were mapped as indicators of vicariance and compared with previously identified biogeographical barriers. Congruent vicariance versus regional richness determined the relative influence of barriers. Patterns of overlap among non‐allopatric sister‐species were mapped and assessed.ResultsCongruent vicariance was detected across six previously described biogeographical barriers: the Amazon and Orinoco rivers, Isthmus of Panama, Hawaiian Archipelago, Indo‐Pacific, and a previously understudied barrier separating the Western Indian Ocean from the Central Indo‐Pacific (CIP) termed the Mid‐Indian Ocean Barrier (MIOB). The MIOB showed the strongest vicariant signal. None of the barriers had significantly more or less relative influence. The majority of sister‐species were non‐allopatric. Overlap was concentrated in an area concordant with the biodiversity hotspot in the CIP, where sister‐pairs had significantly low overlap.Main conclusionsBiogeographical barriers may have influenced vicariance of extant species during the past 5 Myr. Older barriers influenced divergence between clades. Turbidity currents produced by outflow from the Ganges and Indus river systems likely explain the strength of the MIOB. Despite the array of described barriers within the CIP, the Sunda Margin Barrier (SMB) was the only vicariant signal detected in the region. Low relative influence of the SMB and significantly low overlap among non‐allopatric sister‐pairs in the CIP highlights its importance as an area of evolutionary dynamism, where the separation of Indian and Pacific Ocean faunas and their subsequent range expansion has led to increased species overlap and higher regional biodiversity.