On the concept of chorotype

Recent reviews of the meaning of the word ‘chorotype’ in biogeography have led to contrasting definitions and a confusion of concepts. This is because ‘chorotype’ has been used by different authors to express two different concepts: (1) groups of species with overlapping ranges (overall distributions) and (2) groups of species with a similar distribution within a certain area. To avoid confusion, I suggest the term ‘global chorotype’ be used to indicate a group into which species with similar ranges can be classified; and ‘regional chorotype’ be used for a group of species with similar distributions within a certain region. Although the global chorotype represents the world‐wide spatial responses of species to historical and environmental pressures, and does not vary with the area under consideration, a particular species might be classified into different regional chorotypes in different study areas.     

Biogeographical zonation of African hornbills and their biotic and geographic characterisations

We studied the geographic ranges of the 23 African hornbill species using countries as distribution units, to search for either groups of similar distributions (chorotypes) or gradual replacement of species as two different types of distribution patterns. We used a probabilistic classification method to distinguish between these two types of biogeographic patterns. Then we analysed the influence of climate, area, surface covered by different types of habitat, and human disturbance in each country, as well as biotic features of the species involving the habitat preference, feeding requirements and habits, body size, sexual dimorphism, and metabolic parameters, on the biogeographic patterns detected. We found that 20 species were significantly classified into three chorotypes. The western-central chorotype comprises nine species characterised by their preference for forest habitat and their low sexual body mass dimorphism. These species occur in 25 countries, characterised by their low range of temperatures. The eastern chorotype includes three species characterised by their preference for feeding on the ground and greater dimorphism in mass between the sexes. Seven countries, characterised by their high values of savanna and grassland surface area, constitute the geographic element of this chorotype. The southern chorotype involves the distribution of eight species characterised by their preference for montane and coastal forests or woodlands. Eighteen countries fall into this chorotype and are characterised by their low values of temperature in the coldest month and greater surface area of desert scrub and desert forest. The other three species replace each other mainly following a gradual pattern within the study area.     

The Watson–Forbes Biogeographical Controversy Untangled 170 Years Later

Hewett Cottrell Watson and Edward Forbes were two naturalists of the Victorian age. They were protagonists on a dispute that generated comment and serves as an illuminating case study of misunderstanding in priority issues. Watson accused Forbes of having plagiarized his original classification of the British plants into groups on the basis of their geographical distribution. This controversy originated mostly from a so-far-ignored basic difference in Watson’s and Forbes’ ideas about biogeographical regionalization. Watson’s classification of the British flora into groups of species with similar distribution was probably the first application of the concept of “regional chorotype.” By contrast, the biogeographical classification of the British flora proposed by Forbes belongs to the concept of “element,” because it was based on assumed species history (i.e. colonization routes). The two approaches may produce similar outcomes, but remain conceptually different. Although personal reasons may have contributed to exacerbate the Watson–Forbes controversy, failure in recognizing this distinction by its actors and their contemporaries, such as Hooker and Darwin, was the most important cause.     

Body‐size distribution and biogeographical patterns in non‐marine ostracods (Crustacea: Ostracoda)

The idea that free‐living minute organisms have ubiquitous distributions has been recently revitalized, causing significant controversy. The ubiquitous model predicts that a threshold where ubiquity leaves room to biogeography might exist somewhere along the animal body‐size range. In the present study, such a prediction is tested by analysing body‐size frequency distribution, species distribution, and local‐to‐global species ratio at the scale of biogeographical realms in cypridoidean non‐marine ostracods, a group with a body‐size range in the ubiquity–biogeography (U‐B) boundary. Data were gathered for all described extant cypridoidean ostracod species (N = 1761), with body‐size recorded for 1134 of them. Although local‐to‐global species ratios show significant over‐dispersal of small‐body ostracods for the Palaearctic and the Australasian regions, there are explanations alternative to the ‘Everything is Everywhere’ model that can account for such a result. Indicators of taxonomic structure do not support the hypothesis of a random distribution of cypridoidean species among realms. Nevertheless, the strong biogeography signal occurring at a large scale vanishes at the local scale (country‐level within the Palaearctic), and suggests wide dispersion within biogeographical realms. Additional factors, including inconsistent taxonomic criteria for species recognition, uneven sampling effort, and an excess of ‘single‐report’ occurrences, have been identified too as potential distorters of the observed patterns. Taxonomic harmonization, open databases of biogeographical data, and better ecological information are suggested as critical goals that need to be achieved for further understanding of ostracod global distribution patterns. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 409–423.     

Modelling chorotypes of invasive vertebrates in mainland Spain

We investigated the existence of chorotypes – assemblages of species with similar geographical ranges – of invasive species in a host territory, and their potential use to advocate similar control or management strategies for species in the same chorotype. We analysed the distribution of 13 exotic terrestrial vertebrate species (six birds, six mammals, and one reptile) with well‐known distributions in mainland Spain. We used the presence/absence data on a grid of 10 km × 10 km UTM cells from the Atlases of terrestrial vertebrates of Spain. These data were aggregated to a grid of 50 km × 50 km UTM cells, because it entailed no loss of meaningful information and allowed dealing with a much lower number of cells. Using cluster analysis and a probabilistic assessment of the classification, we identified seven significant chorotypes: four multispecific and three monospecific. The compound chorotypes grouped together species that tended to share certain characteristics about their introduction, release cause, establishment, and spread. We modelled the chorotypes using a favourability function based on a generalized linear model and 31 variables related to spatial situation, topography, lithology, climatic stability, energy availability, water availability, disturbances, productivity, and human activity. Climatic factors affected the favourability for every chorotype, whereas human variables had a high influence in the distribution of three chorotypes involving eight species. On the basis of these variables, we identified favourable areas for all the chorotypes in mainland Spain. The favourability for a chorotype in an area may be a useful criterion for evaluating the local conservation concern due to the whole set of species. Favourable but unoccupied areas can be used to infer possible colonization areas for each chorotype. We recommend using chorotypes to optimize broad‐scale surveillance of invasive species.     

Synthesizing traditional biogeography with microbial ecology: the importance of dormancy

The discovery of biogeographical patterns among microbial communities has led to a focus on the empirical evaluation of the importance of dispersal limitation in microbial biota. As a result, the spatial distribution of microbial diversity has been increasingly studied while the synthesis of biogeographical theory with microbial ecology remains undeveloped. To make biogeographical theory relevant to microbial ecology, microbial traits that potentially affect the distribution of microbial diversity need to be considered. Given that many microorganisms in natural environments are in a state of dormancy and that dormancy is an important microbial fitness trait, I provide a first attempt to account for the effects of dormancy on microbial biogeography by treating dormancy as a fundamental biogeographical response. I discuss the effects of dormancy on the equilibrium theory of island biogeography and on the unified neutral theory of biodiversity and biogeography, and suggest how the equilibrium theory of island biogeography can produce predictions approaching those of the Baas‐Becking hypothesis (i.e. everything is everywhere, but the environment selects). In addition, I present a conceptual model of the unified neutral theory of biodiversity and biogeography, generalized to account for dormancy, from which a full model can be constructed for species with or without dormant life history stages.     

Prospects and challenges for parametric models in historical biogeographical inference

In historical biogeography, phylogenetic trees have long been used as tools for addressing a wide range of inference problems, from explaining common distribution patterns of species to reconstructing ancestral geographic ranges on branches of the tree of life. However, the potential utility of phylogenies for this purpose has yet to be fully realized, due in part to a lack of explicit conceptual links between processes underlying the evolution of geographic ranges and processes of phylogenetic tree growth. We suggest that statistical approaches that use parametric models to forge such links will stimulate integration and propel hypothesis-driven biogeographical inquiry in new directions. We highlight here two such approaches and describe how they represent early steps towards a more general framework for model-based historical biogeography that is based on likelihood as an optimality criterion, rather than having the traditional reliance on parsimony. The development of this framework will not be without significant challenges, particularly in balancing model complexity with statistical power, and these will be most apparent in studies of regions with many component areas and complex geological histories, such as the Mediterranean Basin.     

Historical biogeography of New World emballonurid bats (tribe Diclidurini): taxon pulse diversification

Aim To reconstruct the biogeographical history of New World emballonurid bats (tribe Diclidurini). Although bats are the second most species‐rich order of mammals, they have not contributed substantially to our understanding of the historical biogeography of mammals in the Neotropics because of a poor fossil record. In addition, being the only group of mammals that fly, bats typically have large distributions with relatively few species endemic to restricted areas that are amenable to vicariant biogeographical approaches. Location Central and South America. Methods Phylogenetic analysis for comparing trees (PACT) is a new algorithm that incorporates all spatial information from taxon area cladograms into a general area cladogram. There were nine biogeographical areas identified in Central and South America for New World emballonurid bats. Molecular dating was used to incorporate the temporal aspect of historical biogeography. This method was compared with dispersal–vicariance analysis (DIVA), which assumes vicariance as the default mode of speciation. Results Of the 45 speciation events in a fully resolved phylogeny, eight that were hypothesized by DIVA as vicariance were considered by PACT as two peripheral isolations and six within‐area events. DIVA was less parsimonious because it required six more post‐speciation dispersal events in addition to the 73 hypothesized by PACT. DIVA reconstructed a widely distributed ancestor, suggesting that most dispersal events occurred earlier, whereas the ancestral area for PACT based on character optimization was the Northern Amazon, suggesting that dispersal events were more recent phenomena. Main conclusions The general area cladogram from PACT indicated that within‐area events, and not vicariance, provide the major mode of speciation for New World emballonurid bats. There was no biological evidence supporting or rejecting sympatric speciation in New World emballonurid bats. However, the geological history, combined with fluctuations in temperature and sea level, suggested within‐area speciation in a changing and heterogeneous environment in the Northern Amazon during the Miocene. This scenario is similar to the taxon‐pulse hypothesis of biotic diversification, which posits repeated episodes of range expansions and contractions from a stable core area such as the Guiana Shield within the Northern Amazon.     

A review of bipolarity concepts: History and examples from Radiolaria and Medusozoa (Cnidaria)

Bipolarity, its history and general interpretation are investigated and discussed herein. Apart from the classical view, namely that a bipolar distribution is a peculiar biogeographical phenomenon, we propose that it is ecologically controlled too. This approach was used for bipolarity assessment within the following groups: Phaeodaria, Nassellaria, Spumellaria (Radiolaria) and Medusozoa (Cnidaria). We recognize 46 bipolar radiolarian species and three radiolarian genera. However, although species concepts in radiolarians are relatively stable and well known, the high-rank taxonomy of radiolarians is still not well defined. Caution should therefore be taken in the interpretation of distribution data at a taxonomic level higher than the species. In the Medusozoa, bipolarity is observed for 23 species and 32 genera. The different ways in which bipolarity can develop are discussed under the different groups, but preference has been given to the recent and most probable routes of migration. In our investigation of the bipolarity phenomenon, we reviewed more than 400 articles dealing with taxonomy, ecology and biogeography of the modern fauna in both groups.     

Biological images of geological history: through a glass darkly or brightly face to face?

Abstract Aim To explore the implications for historical biogeography of a recent review of island biogeographical theory in three main thematic areas and to suggest ways in which a synthesis between the two approaches might be achieved to the benefit of both. Location The Indo‐Australian tropics. Theme 1 discusses the relationship of species number to area, and how the nestedness of faunas may influence the methodology used for some types of analysis and also the quality of data expected from an archipelago embracing an extreme range of island sizes. Theme 2 examines the way in which the processes of speciation may lead to development of biogeographical patterns through a complex archipelago, illustrated in particular with reference to Sulawesi where biotic enrichment from different lepidopteran groups follows predictions from island biogeographical theory. This also has implications for patterns of endemism in the archipelago, another constraint on the quality of data available for historical biogeography. Theme 3 addresses ecological determinism as an influence in development of biogeographical pattern, focusing on the theme of specificity in insect–plant relationships and the potential for parallel development of pattern in an insect group and its particular plant host group. This theme is developed with particular reference to moth and plant groups that may represent Gondwanan elements in the Oriental fauna, with an analysis of Sarcinodes, a geometrid moth genus associated with Proteaceae. Main conclusions Prospects are assessed for the synthesis of the two approaches of island biogeography and historical biogeography. Modelling pattern development with the former may complement the methods of analysis of the latter, particularly if some satisfactory method for dating events of pattern development can also be incorporated.     

Distribution patterns of the small mammals (Insectivora and Rodentia) in a transitional zone between the Eurosiberian and the Mediterranean regions

To determine, by means of quantitative analyses, the distribution patterns of the insectivores and rodents in Catalonia using physiographical regions as Operative Geographical Units (OGUs). Catalonia (north‐eastern Iberian Peninsula). Based on the presence/absence of twenty‐five small mammals in thirteen physiographical regions, which were used as OGUs, the following aspects were studied: (a) identification of biotic boundaries; (b) determination of chorological association of species; (c) climatic characterization of the biotic regions and the chorotypes. Groups of biotic regions and species were established, and their statistical significance was tested. The possible effect of several climatic factors on these groupings was studied using discriminant analyses. A significant biotic boundary was found to separate the central and eastern Pyrenees from the remaining physiographical regions. The climatic variables that defined this boundary were related to the severity and the availability of environmental energy. Four chorotypes were identified. One chorotype was constituted by Pyrenean or Pre‐Pyrenean species, an association determined by their mid‐European requirements; another chorotype was formed by Eurosiberian species, but showed a variable degree of tolerance to Mediterranean conditions; a third chorotype included species with a wide distribution that are Mediterranean, anthropic, generalist or have very specific habitats; and finally the fourth chorotype was constituted by a strictly Mediterranean species. The climatic factors that accounted for the distribution of these chorotypes were the mean July temperature and the mean annual precipitation. We conclude that the axial zone of the Pyrenees, except the coastal portion, determines two biotic regions in Catalonia. As for the classification of species, using quantitative techniques for the first time, we offer a new biogeographicalal configuration for the small mammals in this temperate‐Mediterranean transition.     

Misconceptions about parsimony analysis of endemicity

Parsimony analysis of endemicity (PAE) has been widely criticized in the recent literature based on methodology rather than on theory. Here I argue that most of the criticisms of PAE result from confusion between the dynamic and static approaches of PAE, by both users and critics of the method. Originally, PAE (the dynamic approach) was proposed primarily for historical comparisons of biotic distributions based on geological and stratigraphical information; that is, the stratigraphical record of the biota within two or more horizons was used to evaluate changes (layer by layer) in their distributional patterns. This led to an analysis of the biota throughout space and through time. On the other hand, the static approach excluded the temporal component and based the analysis on a single geological horizon. Most problems exemplified and discussed in the literature refer to the static approach. In addition to this defence of the original PAE, I present some new criticisms regarding the application of PAE using artificially delimited areas (for example areas defined by geopolitical boundaries), which may lead to incorrect interpretations. Recently, several variations of static PAE have appeared: some designed to accommodate ecological data (e.g. parsimony analysis of distributions – PAD); others that incorporate phylogenetic content (e.g. cladistic analysis of distributions and endemism – CADE); and some that have been integrated with other historical methods (e.g. panbiogeography) in order to detect and evaluate hypotheses of biogeographical homologies. Biogeographers, both ecological and historical, should be aware of the problems and limitations of both dynamic and static PAE and evaluate new variations of PAE (PAD, CADE, etc.). Finally, I argue in favour of an independent and pluralist discipline of biogeography that treats biogeography as related to systematics but not dependent on it, as some scholars have assumed.     

Biogeography of helminth parasites of freshwater fishes in Mexico: the search for patterns and processes

Aim To uncover and describe patterns of biogeography of helminth parasites in freshwater fishes of Mexico, and to understand processes that determine them. Three predictions about host‐specificity, faunal exchange in transitional areas, and the biogeographical ‘core’ fauna, are evaluated, all of which follow from a fundamental hypothesis: that parasites show characteristic associations with particular host clades. The parasite fauna of the southern Mexican cichlids and of the fishes of the Mesa Central are examined as case studies that reflect Neotropical and Nearctic historical influences. Location The region covered in this study includes most of Mexico, with emphasis on six biogeographical areas: the Yucatán Peninsula (area 1), the Grijalva‐Usumacinta drainage (area 2), the Papaloapan and Pánuco drainages (area 3), the Balsas drainage (area 4), the Lerma‐Santiago drainage (area 5), and the Bravo drainage (area 6). Methods A parasite data base containing all the records of helminth parasites of freshwater fishes of Mexico was filtered to extract records of adult helminth parasites in freshwater fishes from the six biogeographical areas designated in this study. Jaccard's similarity coefficients and cluster analyses (using upgma ) were used to analyse the extent of faunal similarity between the designated biogeographical areas and between host (fish) families. Taxonomic composition of parasite assemblages in different host groups was also qualitatively compared from summary data. These data were used to test the three main predictions. Results To date, 184 species of helminths (120 as adults) have been recorded from 127 freshwater fishes in Mexico (almost 33% of the total fish diversity of Mexico). Of these parasite species, 69 are digenetic flukes, 51 are nematodes, 33 are monogeneans, 25 are tapeworms, and only six are acanthocephalans. The data and analyses from the six biogeographical areas corroborate the predictions that: (1) the adult parasite fauna is largely circumscribed by higher levels of monophyletic host taxa (families, orders, etc.), and that this pattern is independent of areas; (2) areas within a certain biogeographical region, and consequently with similar fish composition (e.g. areas 1, 2 and 3) have more similar parasite faunas compared to areas with less similar fish faunal composition; and (3) ‘core’ parasite faunas persist to some extent in transitional areas with limited host‐sharing. Main conclusions Helminth biodiversity in Mexican freshwater fishes is determined by the historical and contemporary biogeography of their hosts. Host lineage specificity, mainly at the level of the host family, appears to be an important factor in the distribution of the parasites. Most fish families (Characidae, Cichlidae, Pimelodidae, Ictaluridae, Catsotomidae, Goodeidae, Atherinidae) possess their own characteristic ‘core’ helminth fauna, with limited host‐sharing in transitional areas (e.g. areas 3 and 4). A re‐evaluation of the helminth fauna of Mexican cichlids questions the hypothesis that cichlids lost parasites during the colonization of Mexico from South America. The evidence supports the idea that they acquired new parasites by host switching, possibly from marine or brackish‐water percomorphs. In contrast, the parasite fauna of the Mesa Central remains enigmatic and reflects the region's history of endemicity with historical marine and Nearctic connections.     

The world's biogeographical regions: cluster analyses based on bat distributions

Aim Both floral kingdoms and faunal regions have so far been intuitively defined. This study was conducted to compare these with an analytical regionalization based on cluster analyses in a fairly homogeneous, globally distributed group of organisms: the bats (order Chiroptera). This comparison was used to discuss the possibilities of employing clustering techniques in global biogeography. Location The study considered bat distributions world‐wide. Methods Analyses were conducted both for presence/absence of genera and species, and for the number of species in each genus. Clusters distinguished at selected dissimilarity values were mapped. Results A set of c. 10 regional clusters recurred in the analyses, broadly corresponding not only to the world's accepted faunal regions and subregions, but also to the floral kingdoms and subkingdoms. Main conclusions This study is an analytical confirmation of the fact that similar global distribution patterns are to be found in different groups of organisms. Cluster analyses can be used to refine global regionalization schemes, and, with the accumulation of such data for different taxa and ecologically defined groups, shared patterns can be used to draft one common global biogeographical regionalization. At the same time, differences between the regionalization schemes derived for different groups can be used to partial out the role of dispersal abilities, body size, evolutionary age, etc., in determining global distribution patterns.     

On biotas and their names

Biogeographers working under different approaches have proposed several terms to refer to biotas, e.g. the flora and fauna of a region, and to name subsets of taxa within such biotas. It is not clear whether they refer exactly to the same entities and which is the most adequate term to refer to them. Ten concepts refer to the set of taxa that inhabit an area at a single temporal plane (concrete biota, chronofauna, area of endemism, nuclear area, phytocorion, centre of endemism, generalized track, biogeographical assemblage, taxonomic assemblage, and species assemblage), whereas another nine concepts refer to subsets of taxa within a biota (biotic element, historical source, historical component, faunal element, cenocron, dispersal pattern, distributional pattern, lineage, and historical biota). Three concepts can be ascribed to both groups, depending on the author considered (horofauna, chorotype and biotic component). I propose to use the terms ‘biota’ and ‘cenocron’ as general terms, within a framework of integrative pluralism. Biotas can be considered individuals, for which the terms area of endemism, generalized track or chorotype can be preferred for specific analyses. Cenocrons incorporate a temporal dimension when implying explicitly or implicitly a different time of their incorporation to the biota.     

The partitioning of Africa: statistically defined biogeographical regions in sub‐Saharan Africa

Aim To test whether it is possible to establish a common biogeographical regionalization for plants and vertebrates in sub‐Saharan Africa (the Afrotropical Region), using objective multivariate methods. Location Sub‐Saharan Africa (Afrotropical Region). Methods We used 1° grid cell resolution databases for birds, mammals, amphibians and snakes (4142 vertebrate species) and c. 13% of the plants (5881 species) from the Afrotropical Region. These databases were analysed using cluster analysis techniques to define biogeographical regions. A β(sim) dissimilarity matrix was subjected to a hierarchical classification using the unweighted pair‐group method with arithmetic averages (UPGMA). The five group‐specific biogeographical regionalizations were compared against a regionalization developed from a combined database, and a regionalization that is maximally congruent with the five group‐specific datasets was determined using a consensus classification. The regionalizations were interpreted against measures of spatial turnover in richness and composition for the five datasets as well as the combined dataset. Results We demonstrate the existence of seven well‐defined and consistent biogeographical regions in sub‐Saharan Africa. These regionalizations are statistically defined and robust between groups, with minor taxon‐specific biogeographical variation. The proposed biogeographical regions are: Congolian, Zambezian, Southern African, Sudanian, Somalian, Ethiopian and Saharan. East Africa, the West African coast, and the transitions between the Congolian, Sudanian and Zambezian regions are unassigned. The Cape area in South Africa, Afromontane areas and the coastal region of East Africa do not emerge as distinct regions but are characterized by high neighbourhood heterogeneity, rapid turnover of species and high levels of narrow endemism. Main conclusions Species distribution data and modern cluster analysis techniques can be used to define biogeographical regions in Africa that reflect the patterns found in both vertebrates and plants. The consensus of the regionalizations between different taxonomic groups is high. These regions are broadly similar to those proposed using expert opinion approaches. Some previously proposed transitional zones are not recognized in this classification.     

Distributional patterns of Neotropical seasonally dry forest birds: a biogeographical regionalization

Neotropical seasonally dry forests (NSDFs) are widely distributed and possess high levels of species richness and endemism; however, their biogeography remains only partially understood. Using species distribution modelling and parsimony analysis of endemicity, we analysed the distributional patterns of the NSDF avifauna in order to identify their areas of endemism and provide a better understanding of the historical relationships among those areas. The strict consensus trees revealed 17 areas of endemism for NSDFs, which involve four large regions: Baja California, Caribbean–Antilles islands, Mesoamerica and South America. These well-resolved clades are circumscribed by geographical and ecological barriers associated with the Gulf of California, the leading edge of the Caribbean plate, the Tehuantepec Isthmus, the Polochic–Motagua fault, the Nicaragua Depression, the Chocó forest, the Amazon basin and the Andean Cordillera. Relationships among groups of NSDFs found here suggest that evolution of their avifauna involved a mixture of vicariance and dispersal events. Our results support the idea of independent diversification patterns and biogeographical processes in each region, including those previously associated with the Pleistocene Arc Hypothesis for NSDFs of south-eastern South America. This study provides a biogeographical framework to open new lines of research related to the biotic diversification of NSDFs.     

Determinants of regional species richness: an empirical analysis of the number of hawkmoth species (Lepidoptera: Sphingidae) on the Malesian archipelago

Aims Major patterns and determinants of the species richness of Sphingidae in the Malesian archipelago were investigated, including a distinction of richness patterns between subfamilies and range‐size classes. Location Southeast Asia, Malesia. Methods Using a compilation of specimen‐label data bases, geographic information system (GIS)‐supported estimates of distributional ranges for all Sphingidae species of Southeast Asia were used to assess the species richness of islands. Range maps for all species and checklists for 114 islands can be found at http://www.sphingidae‐sea.biozentrum.uni‐wuerzburg.de . Potential determinants of the species richness of islands were tested with general linear models. Results The estimated species richness of islands in the region is determined by biogeographical association, seasonality, availability of rain forest and island size. Species–area relationships are linear on a semi‐logarithmic representation, but not on a double‐logarithmic scale. Species richness of all sphingid subfamilies is influenced by biogeography. The presence of large rain‐forest areas affects mainly Smerinthinae, whereas distance from continental Asia is conspicuously irrelevant for this group. Widespread rather than geographically restricted species shape the overall distribution patterns of species richness. The altitudinal range of islands does not significantly affect species‐richness patterns, but its potential effects on geographically restricted species are discussed. Main conclusions As well as being affected by climatic and vegetation parameters, sphingid species richness is strongly influenced by a historical, directional dispersal process from continental Southeast Asia to the Pacific islands. This process did not apply equally to species of different taxonomic groups or range sizes. Widespread species decline in species richness towards the south‐east, whereas geographically restricted species exhibit an inverse pattern of species richness, probably because speciation becomes more important in this group within the more isolated island groups.     

The biogeography of seaweeds in Southeast Alaska

Aim This article reviews the history of seaweed collections in Southeast Alaska from the early Russian explorers to contemporary efforts. It summarizes other studies of Southeast Alaskan seaweeds from a biogeographical perspective, and compares the known seaweed flora near three population centres (Ketchikan, Sitka and Juneau) with those of other regions within Alaska, and with nearby regions. Location For this article, Southeast Alaska includes all inside and outside waters of the Alexander Archipelago from Dixon Entrance (54°40′ N, 133°00′ W) to Icy Point (58°23′10″ N, 137°04′20″ W). Methods The literature on seaweeds occurring in Southeast Alaska is reviewed from a biogeographical perspective, and herbarium records for Southeast Alaska from the Alaska Seaweed Database project are used to provide an overview of the biogeography of the area. Records for the population centres of Ketchikan, Sitka and Juneau are compared with records from other areas within Alaska and with nearby regions to determine floristic similarities. Results Southeast Alaska has the most diverse seaweed flora of any region of Alaska. A list of species known to occur in Southeast Alaska is appended (in Supplementary Material) and includes their reported occurrences in three population centres (Juneau, Ketchikan and Sitka). Recognition of at least three distinct biogeographical areas associated with these three centres is supported by a comparison of their floras with those of other regions in the North Pacific. A close relationship of some species with conspecifics in the north‐west Atlantic is also noted. In contrast, ecological, physiological and genetic differentiation of Southeast Alaskan seaweeds from conspecifics in Washington State or even from different areas of Southeast Alaska are documented. A ShoreZone coastal habitat system, which is being implemented to inventory and map the entire shoreline of Southeast Alaska, is defining new biogeographical units called ‘bioareas’ on the basis of the distribution of canopy kelps and lower intertidal algal assemblages. Main conclusions Southeast Alaska has the most diverse seaweed flora of any region of Alaska. This is a reflection of its extensive coastline, with varied past and present environmental conditions. Different parts of Southeast Alaska show similarities to different areas outside Southeast Alaska. Despite this, much remains to be learned about the biogeography of seaweeds in Southeast Alaska, and many questions remain to be answered.