Frontiers of Biogeography

Species are the currency of most biodiversity studies. However, many shortfalls and biases remain in our biodiversity estimates, preventing a comprehensive understanding of the eco-evolutionary processes that have shaped the biodiversity currently available on Earth. Biased biodiversity estimates also jeopardize the effective implementation of data-driven conservation strategies, ultimately leading to biodiversity loss. Here, we delve into the concept of the Latitudinal Taxonomy Gradient (LTG) and show how this new idea provides an interesting conceptual link between the Linnean (i.e., our ignorance of how many species there are on Earth), Darwinian (i.e., our ignorance of species evolutionary relationships), and Wallacean (i.e., our ignorance on species distribution) shortfalls. More specifically, we contribute to an improved understanding of LTGs and establish the basis for the development of new methods that allow us to: (i) better account for the integration between different shortfalls and, (ii) estimate how these interactions may affect our understanding about the evolutionary components of richness gradients at macroecological scales.

The Indo-Australian Archipelago (IAA) is a geologically dynamic area of high biotic endemism that spans the continental shelves of Sunda and Sahul and intervening oceanic islands. We provide a comprehensive quantitative assessment of how bird communities are structured across the IAA using beta diversity indices. We focus on three key questions. Are the islands of Wallacea a biogeographically cohesive unit or a more heterogeneous transition zone? Is the rich biota of New Guinea and the East Melanesian islands most closely linked to that of Sunda, Sahul or Wallacea? What are the geographic and environmental correlates of biotic structuring across the region and how does this compare with determinants of plant diversity? We measure the dissimilarity of bird species composition between eleven major areas within the IAA using a new compilation of distribution data and calculate taxonomic beta diversity at species, genera, and family levels. To compare with recent analyses of plants, we analysed potential correlates of turnover, focusing on geographic proximity, sea barriers, land area, and climatic variation. We also used connectivity analyses to estimate the minimum number of connection events needed to explain the current distribution of shared taxa. We found that islands recently connected by land have lower beta diversity than oceanic islands. Additionally, avifaunas on the islands of Wallacea have little biotic cohesion, reflecting their complex geological history. The avifaunas of New Guinea and the Eastern Melanesian islands are very distinctive. Where New Guinea birds are most similar to Australia, East Melanesian birds are more similar to either Sahul or Wallacea, depending on taxonomic level. Isolation through space and time had the strongest influence on avifaunal turnover at all taxonomic scales, in contrast to plants for which climatic variation was the strongest predictor. Further analyses incorporating phylogeny, biome, trait, and biotic interaction data are needed to investigate the processes that have caused biotic turnover across this fascinating biogeographic region.

Knowledge on biodiversity is fundamental for conservation strategies. The Brazilian Pampa region, located in subtropical southern Brazil, is neglected in terms of conservation, and knowledge of its biodiversity is fragmented. We aim to answer the question: how many, and which, species occur in the Brazilian Pampa? In a collaborative effort, we built species lists for plants, animals, bacteria, and fungi that occur in the Brazilian Pampa. We included information on distribution patterns, main habitat types, and conservation status. Our study resulted in referenced lists totaling 12,503 species (12,854 taxa, when considering infraspecific taxonomic categories [or units]). Vascular plants amount to 3,642 species (including 165 Pteridophytes), while algae have 2,046 species (2,378 taxa) and bryophytes 316 species (318 taxa). Fungi (incl. lichenized fungi) contains 1,141 species (1,144 taxa). Animals total 5,358 species (5,372 taxa). Among the latter, vertebrates comprise 1,136 species, while invertebrates are represented by 4,222 species. Our data indicate that, according to current knowledge, the Pampa holds approximately 9% of the Brazilian biodiversity in an area of little more than 2% of Brazil’s total land. The proportion of species restricted to the Brazilian Pampa is low (with few groups as exceptions), as it is part of a larger grassland ecoregion and in a transitional climatic setting. Our study yielded considerably higher species numbers than previously known for many species groups; for some, it provides the first published compilation. Further efforts are needed to increase knowledge in the Pampa and other regions of Brazil. Considering the strategic importance of biodiversity and its conservation, appropriate government policies are needed to fund studies on biodiversity, create accessible and constantly updated biodiversity databases, and consider biodiversity in school curricula and other outreach activities.

The mopane worm (Gonimbrasia belina) is an edible insect distributed across southern Africa. As a culturally important source of food, the mopane worm provides nutrition, livelihoods and improves wellbeing for rural communities across its range. However, this is strong evidence that insect populations are declining worldwide, and climate change is likely to cause many insect species to shift in their distributions. For these reasons, we aimed to model how the ecosystem service benefits of the mopane worm are likely to change in the coming decades. We modelled the distribution of the mopane worm under two contrasting climate change scenarios (RCPs 4.5 and 8.5). Moreover, given that the mopane worm shows strong interactions with other species, particularly trees, we incorporated biotic interactions in our models using a Bayesian network. Our models project significant contraction across the species’ range, with up to 70% decline in habitat by the 2080s. Botswana and Zimbabwe are predicted to be the most severely impacted countries, with almost all habitat in Botswana and Zimbabwe modelled to be lost by the 2080s. Decline of mopane worm habitat would likely have negative implications for the health of people in rural communities due to loss of an important source of protein as well as household income provided by their harvest. Biogeographic shifts therefore have potential to exacerbate food insecurity, socio-economic inequalities, and gender imbalance (women are the main harvesters), with cascading effects that most negatively impact poor rural communities dependent on natural resource

Information on the paleo-beta diversity of fossil assemblages and its patterning in different geological time intervals helps us to better understand the community level response of biodiversity patterns to current global warming. We focused on the impact of paleoclimate changes on large-scale taxonomic sorting related to geography; specifically, how cooler and warmer climatic conditions affect the distance-dependency of beta diversity. Using a dataset of Cenozoic fossil assemblages of angiosperm woody plants (7,468 data points; 310 genera in 95 families) in the Japanese portion of the East Asian archipelago (except Ryukyu islands), we modeled the distance-dependency of genus turnover (pairwise compositional dissimilarity) through the Oligocene, Miocene, Pliocene, Pleistocene, Last Glacial Period, Holocene, and present day. The genus turnover of angiosperm woody plants was significantly correlated with geographical and climatic distance only in the Last Glacial Period, Holocene, and present day. During the Oligocene to Pliocene, the warm periods, genus turnover was mostly independent of geographical distance. Spatial/climatic distance-dependent turnover under colder environments involved a climate-induced sorting process to spatially diversify woody-plant assemblages across the archipelago. Moreover, the predominance of distant-independent turnover suggested the effect of dispersal release under warmer, stable climates. Our findings suggest that future tropicalization in temperate habitats could promote geographical homogenization of biodiversity patterns.

The Marine Ecoregions of the World system separates the oceans into 232 ecoregions based on coastal and shelfwater species distributions. We tested the separation of those ecoregions and delineated subecoregions within Western Australian waters using intertidal macroalgal and epiphytic polychaete distributions. Environmental predictors of those assemblages were also determined. We collected macroalgae and polychaetes on 38 rocky intertidal shores within four marine ecoregions from 18°S to 34°S: (1) Exmouth to Broome, (2) Ningaloo, (3) Houtman, and (4) Leeuwin. We evaluated differences in species composition of macroalgae and polychaetes among those ecoregions using pairwise permutational multivariate analysis of variance and delineated subecoregions within each ecoregion using hierarchical cluster analysis. Multivariate relationships between environmental variables and assemblages were determined using distance-based linear models. The species composition of macroalgae and polychaetes significantly differed among ecoregions, with dissimilarity of 78-96% for macroalgae and 62-75% for polychaetes. We identified three subecoregions within Exmouth to Broome and Ningaloo and two subecoregions within Houtman and Leeuwin based on macroalgal distribution. We also found two subecoregions within Houtman and no subecoregion within Exmouth to Broome, Ningaloo, and Leeuwin based on polychaete distribution. Environmental predictors could explain 51% of the total variation of macroalgae and 41% of the total variation of polychaetes. The top two predictors explaining a high proportion of assemblage distribution were sea surface temperature (15% for macroalgae and 12% for polychaetes) and tidal amplitude (10% for macroalgae and 6% for polychaetes). These ecoregions and subecoregions can be used as an alternative spatial framework for classifying rocky intertidal habitats for designing marine protected area networks within Western Australian waters.

Approximately 3,800 species of vascular plant species have been registered in the flora of Armenia, of which chromosome numbers are known for 798. Additionally, many species have several cytoraces in Armenia (a total of 904 cytoraces have been recorded). The main goal of the study was to elucidate some specific features of florogenesis on the basis of karyological data, and the aim is to characterize the distributions of the cytoraces across floristic regions of Armenia, including elevational zones, and habitats. The study is underpinned by results of our long-term study of Armenian flora, which entailed comprehensively characterizing their chromosome numbers and karyotypes. Geographical elements were established based on general distribution. As a result of the analysis, it was found that the Armenian flora was formed over a long period, starting from the Paleocene period, and is composed of nearly equal proportions of migrants from the Boreal and Ancient Mediterranean subkingdoms, and species that evolved in the Armenian Highlands and in the Greater Caucasus. The possession of a significant percentage of endemics (mainly neoendemics) indicates that the territory of Armenia is also an arena of intensive formation and speciation. In addition, we also illuminated a large karyological diversity among species whose distribution is confined to the Ancient Mediterranean subkingdom or its parts, including the Armeno-Iranian province; this is indicative of speciation having occurred in these territories. The “northern root” species, Boreal and Caucasian, became establish in Armenia mainly in the form of karyologically stable cytoraces.