Assessing Modes of Speciation: Range Asymmetry and Biogeographical Congruence

Lynch [1989, in "Speciation and Its Consequences" (D. Otte and J. A. Endler, Eds.), pp. 527–553, Sinauer, Sunderland, MA, proposed a methodology for assessing the frequency of occurrence of various modes of initiating species formation, using a combination of phylogenetic relationships and relative size of geographic ranges for sister species and sister groups. Historical biogeography provides an alternative criterion for assessing modes of species formation. Species whose distributions conform to a general (replicated in multiple clades) pattern of area relationships are deemed to be the result of vicariance (including microvicariance) regardless of the details of current geographic range. Species exhibiting unique biogeographic distributions are the result of peripheral isolates speciation and postspeciation dispersal. Lineage duplications indicate sympatric speciation. An empirical assessment of this alternative approach was performed using the most recent phylogenetic trees and geographical distribution data on the Mesoamerican poeciliid fish comprising the genera Xiphophorus and Heterandria . The single area cladogram produced by secondary Brooks Parsimony Analysis indicates 3 vicariant events (accounting for seven extant species and the common ancestor of the northern swordtails, which are not further analyzed) and at least 13 episodes of peripheral isolates speciation. Two of the 10 areas considered in previous analyses are vicariant areas of endemism, 1 is historically unique due to a single episode of peripheral isolates speciation, and the remaining 7 have reticulated histories of speciation. The results corroborate inferences of speciation modes made by Lynch for the same data.     

Patterns of speciation in the genus Lopidea (Heteroptera: Miridae: Orthotylinae)

Abstract. Speciation in four monophyletic species groups of the mirid genus Lopidea is examined. An analysis of twelve speciation events suggests that vicariance can account for at least 50% of speciation in Lopidea , and the frequency of sympatric host plant speciation may be as high as 25%.
In examples attributable to peripheral isolate speciation, the daughter taxa typically occur in recognized areas of endemism, suggesting a common cause (vicariance) for their origins. In addition, seven zones of disjunction between subspecies and allopatric sister species were identified for Lopidea , which correspond with similar disjunctions between sister taxa in other groups of organisms.     

Distribution patterns and biogeographic analysis of Austral Polychaeta (Annelida)

Aim We investigate the biogeography of Austral Polychaeta (Annelida) using members of the families Eunicidae, Lumbrineridae, Oenonidae, Onuphidae, Serpulidae and Spionidae and Parsimony Analysis of Endemicity (PAE). We determine whether observed polychaete distribution patterns correspond to traditional shallow-water marine areas of endemism, estimate patterns of endemism and relationships between areas of endemism, and infer the biological processes that have caused these patterns. Location The study is concerned with extant polychaete taxa occupying shallow-water areas derived from the breakup of the Gondwana landmass (i.e. Austral areas). Methods Similarity was assessed using a significance test with Jaccard's indices. Areas not significantly different at 0.99 were combined prior to the PAE. Widespread species and genera (155 taxa) were scored for presence/absence for each area of endemism. PAE was used to derive hypotheses of area relationships. Hierarchical patterns in the PAE trees were identified by testing for congruence with patterns derived from cladistic biogeographic studies of other Gondwanan taxa and with geological evidence. Results The polychaete faunas of four area-pairs were not significantly different and the areas amalgamated: South-west Africa and South Africa, New Zealand South Island and Chatham Islands, Macquarie Island and Antipodean Islands, and West Antarctica and South Georgia. Areas with the highest levels of species endemism were southern Australia (67.0%), South-east South America (53.2%) and South Africa (40.4%). About 60% of species and 7.5% of genera occupied a single area of endemism. The remainder were informative in the PAE. Under a no long-distance dispersal assumption a single minimal-length PAE tree resulted (l=367; ci=0.42); under dispersal allowed, three minimal-length trees resulted (l=278; ci=0.56). In relation to the sister grouping of the New Zealand areas and Australia we find congruence between our minimal-length trees and those derived from a biogeographic study of land plants, and with area relationships predicted by the Expanding Earth Model. Main conclusions The polychaete distribution patterns in this study differ slightly from the classical areas of endemism, most notably in being broader, thereby bringing into question the value of using single provincial system for marine biogeographic studies. The Greater New Zealand region is found to be ‘monophyletic’ with respect to polychaetes, that is comprising a genuine biogeographical entity, and most closely related to the polychaete fauna of southern Australia. This finding is consistent with studies of land plants and with the Expanding Earth model, but disagrees with conventional geology and biogeographic hypothesis involving a ‘polyphyletic’ New Zealand. Both vicariance and concerted range expansion (=biotic dispersion) appear to have played important roles in shaping present-day distribution patterns of Austral polychaetes. Shallow-water ridge systems between the Australian and Greater New Zealand continental landmasses during the Tertiary are thought to have facilitated biotic dispersion.     

Erratum to: Recent range-wide demographic expansion in a Taiwan endemic montane bird,Steere's Liocichla (Liocichla steerii)

Background  

The subtropical island of Taiwan is an area of high endemism and a complex topographic environment. Phylogeographic studies indicate that vicariance caused by Taiwan's mountains has subdivided many taxa into genetic phylogroups. We used mitochondrial DNA sequences and nuclear microsatellites to test whether the evolutionary history of an endemic montane bird, Steere's Liocichla (Liocichla steerii), fit the general vicariant paradigm for a montane organism.     

Vicariance and endemism in a Neotropical savanna hotspot: distribution patterns of Cerrado squamate reptiles

Aim To test predictions of the vicariance model, to define basic biogeographical units for Cerrado squamates, and to discuss previous biogeographical hypotheses. Location Cerrado; South American savannas south of the Amazon, extending across central Brazil, with marginal areas in Bolivia and Paraguay and isolated relictual enclaves in adjacent regions. Methods We compiled species occurrence records via field sampling and revision of museum specimens and taxonomic literature. All species were mapped according to georeferenced locality records, and classified as (1) endemic or non‐endemic, (2) typical of plateaus or depressions, and (3) typical of open or forested habitats. We tested predictions of the vicariance model using biotic element analysis, searching for non‐random clusters of species ranges. Spatial congruence of biotic elements was compared with putative areas of endemism revealed by sympatric restricted‐range species. Effects of topographical and vegetational mosaics on distribution patterns were studied according to species composition in biotic elements and areas of endemism. Results We recorded 267 Cerrado squamates, of which 103 (39%) are endemics, including 20 amphisbaenians (61% endemism), 32 lizards (42%) and 51 snakes (32%). Distribution patterns corroborated predictions of the vicariance model, revealing groups of species with significantly clustered ranges. An analysis of endemic species recovered seven biotic elements, corroborating results including non‐endemics. Sympatric restricted‐range taxa delimited 10 putative areas of endemism, largely coincident with core areas of biotic elements detected with endemic taxa. Distribution patterns were associated with major topographical and vegetational divisions of the Cerrado. Endemism prevailed in open, elevated plateaus, whereas faunal interchange, mostly associated with forest habitats, was more common in peripheral depressions. Main conclusions Our results indicate that vicariant speciation has strongly shaped Cerrado squamate diversity, in contrast to earlier studies emphasizing faunal interchange and low endemism in the Cerrado vertebrate fauna. Levels of squamate endemism are higher than in any other Cerrado vertebrate group. The high number of recovered endemics revealed previously undetected areas of evolutionary relevance, indicating that biogeographical patterns in the Cerrado were poorly represented in previous analyses. Although still largely undocumented, effects of vicariant speciation may be prevalent in a large fraction of Cerrado and Neotropical biodiversity.     

The trans-Pacific zipper effect: disjunct sister taxa and matching geological outlines that link the Pacific margins

Aim To combine analyses of trans‐Pacific sister taxa with geological evidence in order to test the hypothesis of the existence of a Panthalassa superocean. Location The study is concerned with taxa, both fossil and extant, from East Asia, Australia, New Zealand, South America and North America. Methods Phylogenetic and distributional analyses of trans‐Pacific biota were integrated with geological evidence from the Pacific and circum‐Pacific regions. Results A series of recent biogeographical analyses delineates a zipper‐like system of sister areas running up both margins of the Pacific, with each section of western North and South America corresponding to a particular section from East Asia/Australia/New Zealand. These sister areas coincide neatly with a jigsaw‐like fit provided by the matching Mesozoic coastlines that bracket the Pacific. Main conclusions The young age (<200 Myr) of oceanic crust, the matching Mesozoic circum‐Pacific outlines, and a corresponding system of interlocking biogeographical sister areas provide three independent avenues of support for a closed Pacific in the Upper Triassic–Lower Jurassic. The hypothesis of the existence and subsequent subduction of the pre‐Pacific superocean Panthalassa is not only unnecessary, it conflicts with this evidence. Panthalassa‐based paleomaps necessitate the invention of dozens of additional hypotheses of species‐dependent, trans‐oceanic dispersal events, often involving narrow‐range taxa of notoriously limited vagility, in order to explain repeated examples of the same biogeographical pattern. Removing the vanished‐superocean hypothesis reunites both the matching geological outlines and all the disjunct sister taxa. In brief, what appears to be a multi‐era tangle of convoluted, trans‐oceanic distributions on Panthalassa‐based paleomaps is actually a relatively simple biogeographical pattern that is explainable by a single vicariant event: the opening and expansion of the Pacific.     

Detecting areas of endemism with a taxonomically diverse data set: plants,mammals, reptiles,amphibians, birds,and insects from Argentina

The idea of an area of endemism implies that different groups of plants and animals should have largely coincident distributions. This paper analyses an area of 1152 000 km², between parallels 21 and 32°S and meridians 70 and 53°W to examine whether a large and taxonomically diverse data set actually displays areas supported by different groups. The data set includes the distribution of 805 species of plants (45 families), mammals (25 families), reptiles (six families), amphibians (five families), birds (18 families), and insects (30 families), and is analysed with the optimality criterion (based on the notion of endemism) implemented in the program NDM/VNDM. Almost 50% of the areas obtained are supported by three or more major groups; areas supported by fewer major groups generally contain species from different genera, families, or orders. © The Willi Hennig Society 2011.     

THE BIOGEOGRAPHY OF SULAWESI REVISITED: IS THERE EVIDENCE FOR A VICARIANT ORIGIN OF TAXA ON WALLACE'S “ANOMALOUS ISLAND”?

Sulawesi, the largest island in the Indonesian biodiversity hotspot region Wallacea, hosts a diverse endemic fauna whose origin has been debated for more than 150 years. We use a comparative approach based on dated phylogenies and geological constraints to test the role of vicariance versus dispersal in the origin of Sulawesi taxa. Most divergence time estimates for the split of Sulawesi lineages from their sister groups postdate relevant tectonic vicariant events, suggesting that the island was predominantly colonized by dispersal. Vicariance cannot be refuted for 20% of the analyzed taxa, though. Although vicariance across Wallace's Line was only supported for one arthropod taxon, divergence time estimates were consistent with a "tectonic dispersal" vicariance hypothesis from the East in three (invertebrate and vertebrate) taxa. Speciation on Sulawesi did not occur before the Miocene, which is consistent with geological evidence for more extensive land on the island from that time. The Pliocene onset of periodic sea-level changes may have played a role in increasing the potential for dispersal to Sulawesi. A more extensive taxon sampling in Wallacea will be crucial for refining our understanding of the region's biogeography and for testing hypotheses on the origin of taxa on its most important island.     

Cladistic analysis of distributions and endemism (CADE): using raw distributions of birds to unravel the biogeography of the South American aridlands

Aim To use published distributional and taxonomic information on Neotropical birds in a cladistic analysis of distributions and endemism (CADE) to generate a testable hypothesis of area‐relationships for the arid areas of endemism, particularly those of Central South America (the ‘arid diagonal’), and to clarify the different methodologies commonly associated with parsimony analysis of endemicity (PAE). Location South America. Methods Cladistic analysis of distributions and endemism. Results We obtain a tree where the relationships of most areas are resolved, and we find support for an exclusive clade of Central South American areas, with the Caatinga as sister to both the Chaco and Cerrado. Main conclusions There is a substantial amount of historical signal in avian distributions, when large numbers of taxa and multiple taxonomic levels are considered. Ecological noise and historical information are more easily distinguished in CADE analyses than they would be in PAE analyses. Based on our results we predict that among aridland birds, the Cerrado and Chaco species will be more closely related to each other than to Caatinga species.     

The endemic gastropod fauna of Lake Titicaca: correlation between molecular evolution and hydrographic history

Lake Titicaca, situated in the Altiplano high plateau, is the only ancient lake in South America. This 2- to 3-My-old (where My is million years) water body has had a complex history that included at least five major hydrological phases during the Pleistocene. It is generally assumed that these physical events helped shape the evolutionary history of the lake's biota. Herein, we study an endemic species assemblage in Lake Titicaca, composed of members of the microgastropod genus Heleobia, to determine whether the lake has functioned as a reservoir of relic species or the site of local diversification, to evaluate congruence of the regional paleohydrology and the evolutionary history of this assemblage, and to assess whether the geographic distributions of endemic lineages are hierarchical. Our phylogenetic analyses indicate that the Titicaca/Altiplano Heleobia fauna (together with few extralimital taxa) forms a species flock. A molecular clock analysis suggests that the most recent common ancestor (MRCAs) of the Altiplano taxa evolved 0.53 (0.28-0.80) My ago and the MRCAs of the Altiplano taxa and their extralimital sister group 0.92 (0.46-1.52) My ago. The endemic species of Lake Titicaca are younger than the lake itself, implying primarily intralacustrine speciation. Moreover, the timing of evolutionary branching events and the ages of two precursors of Lake Titicaca, lakes Cabana and Ballivián, is congruent. Although Lake Titicaca appears to have been the principal site of speciation for the regional Heleobia fauna, the contemporary spatial patterns of endemism have been masked by immigration and/or emigration events of local riverine taxa, which we attribute to the unstable hydrographic history of the Altiplano. Thus, a hierarchical distribution of endemism is not evident, but instead there is a single genetic break between two regional clades. We also discuss our findings in relation to studies of other regional biota and suggest that salinity tolerance was the most likely limiting factor in the evolution of Altiplano species flocks.     

Phylogeny of the Neotropical killifish family Rivulidae (Cyprinodontiformes, Aplocheiloidei) inferred from mitochondrial DNA sequences

Phylogenetic relationships of 70 taxa representing 68 species of the Neotropical killifish family Rivulidae were derived from analysis of 1516 nucleotides sampled from four different segments of the mitochondrial genome: 12S rRNA, 16S rRNA, cytochrome oxidase I, and cytochrome b. The basal bifurcation of Cynolebiatinae and Rivulinae (Costa, 1990a,b) is supported; however, Terranatos, Maratecoara, and Plesiolebias are rivulins, not cynolebiatins. These three genera, along with the other recognized annual rivulin genera, form a monophyletic clade. Austrofundulus, Rachovia, Renova, Terranatos, and 3 species of the genus Pterolebias, all from northeastern South America, form a monophyletic clade excluding other species of Pterolebias. Pterolebias as presently understood is clearly polyphyletic. Trigonectes and Moema are supported as sister groups but do not form a monophyletic group with the genera Neofundulus and Renova as previously proposed. The suite of adaptations necessary for an annual life history has clearly been lost several times in the course of rivulid evolution. Also revealed is a considerable increase in substitution rate in most annual lineages relative to the nonannual Rivulus species. The widespread and speciose genus Rivulus is paraphyletic, representing both basal and terminal clades within the Rivulidae. Previous hypotheses regarding the vicariant origin of Greater Antillean Rivulus species are supported. Most rivulid clades show considerable endemism; thus, detailed analysis of rivulid phylogeny and distribution will contribute robust hypotheses to the clarification of Neotropical biogeography.     

THE ZOOGEOGRAPHY AND CENTERS OF ORIGIN OF THE CRAYFISH SUBGENUS PROCERICAMBARUS (DECAPODA: CAMBARIDAE)

The Central Highlands region in the central United States is a taxonomically diverse region with a high incidence of stream endemism. Based on the distributions of the diverse ichthyofauna in the region, a pre-Pleistocene pattern of diversity due to vicariant events has been proposed to explain high levels of endemism and species richness. We tested this hypothesis using crayfish phylogenies and distributional patterns for species distributed in the Central Highlands region. We concluded that both pre-Pleistocene and Pleistocene hypotheses are compatible with the crayfish distributions and these distributions are likely due to a combination of both vicariant and dispersal events. Furthermore, we suggest a Pleistocene center of origin for the crayfish subgenus Procericambarus within the Ozark region and a pre-Pleistocene center of origin for the genus Orconectes within the Eastern Highlands region.     

The geography and ecology of plant speciation: range overlap and niche divergence in sister species

A goal of evolutionary biology is to understand the roles of geography and ecology in speciation. The recent shared ancestry of sister species can leave a major imprint on their geographical and ecological attributes, possibly revealing processes involved in speciation. We examined how ecological similarity, range overlap and range asymmetry are related to time since divergence of 71 sister species pairs in the California Floristic Province (CFP). We found that plants exhibit strikingly different age-range correlation patterns from those found for animals; the latter broadly support allopatric speciation as the primary mode of speciation. By contrast, plant sisters in the CFP were sympatric in 80% of cases and range sizes of sisters differed by a mean of 10-fold. Range overlap and range asymmetry were greatest in younger sisters. These results suggest that speciation mechanisms broadly grouped under ‘budding’ speciation, in which a larger ranged progenitor gives rise to a smaller ranged derivative species, are probably common. The ecological and reproductive similarity of sisters was significantly greater than that of sister–non-sister congeners for every trait assessed. However, shifts in at least one trait were present in 93% of the sister pairs; habitat and soil shifts were especially common. Ecological divergence did not increase with range overlap contrary to expectations under character displacement in sympatry. Our results suggest that vicariant speciation is more ubiquitous in animals than plants, perhaps owing to the sensitivity of plants to fine-scale environmental heterogeneity. Despite high levels of range overlap, ecological shifts in the process of budding speciation may result in low rates of fine-scale spatial co-occurrence. These results have implications for ecological studies of trait evolution and community assembly; despite high levels of sympatry, sister taxa and potentially other close relatives, may be missing from local communities.     

Higher taxa and the identification of areas of endemism

Quantitative analyses of areas of endemism have rarely considered higher taxa. This paper discusses aspects related to the use of higher taxa in the analysis of areas of endemism, and computer implementations. An example of the application of the method is provided, with a data set for Nearctic mammals, showing that some of the areas recognized by species‐level taxa also adjust well to the distribution of other taxa of higher level (genera, monophyletic groups).     

The living heart: Climate gradients predict desert mountain endemism

Mountain regions are centers of biodiversity endemism at a global scale but the role of arid‐zone mountain ranges in shaping biodiversity patterns is poorly understood. Focusing on three guilds of taxa from a desert upland refugium in Australia, we sought to determine: (a) the relative extent to which climate, terrain or geological substrate predict endemism, and (b) whether patterns of endemism are complimentary across broad taxonomic guilds. We mapped regional endemism for plants, land snails, and vertebrates using combined Species Distribution Models (SDMs) for all endemic taxa (n = 82). We then modelled predictors of endemism using Generalised Additive Models (GAMs) and geology, terrain, and climate variables. We tested for the presence of inter‐ and intraguild hotspots of endemism. Many individual plant and land snail taxa were tightly linked with geology, corresponding to small distributions. Conversely, most vertebrate taxa were not constrained to specific geological substrates and occurred over larger areas. However, across all three guilds climate was the strongest predictor of regional endemism, particularly for plants wherein discrete hotspots of endemism were buffered from extreme summer temperatures. Land snail and vertebrate endemism peaked in areas with highest precipitation in the driest times of the year. Hotspots of endemism within each guild poorly predicted endemism in other guilds. We found an overarching signal that climatic gradients play a dominant role in the persistence of endemic taxa in an arid‐zone mountain range system. An association with higher rainfall and cooler temperatures indicates that continuing trends toward hotter and drier climates may lead to range contractions in this, and potentially other, arid‐zone mountain biotas. Contrasting patterns of endemism across guilds highlight the need to couple comprehensive regional planning for the protection of climate refugia, with targeted management of more localized and habitat specialist taxa.     

Dragging into the open: the polythetic nature of areas of endemism

Areas of endemism represent territories (no matter the size) of non-random overlap in the geographic distribution of two or more taxa, reflecting a common spatial history of these taxa. The common spatial history is a result of different processes that connect areas of endemism to evolutionary theory. Numerous and diverse definitions of areas of endemism have been proposed. All of them have used as the conceptual foundation of the definition a certain degree of non-random congruence of geographic distribution amongst at least two taxa. ‘Certain degree’ means that geographic congruence does not demand complete agreement on the boundaries of those taxa's distributions at all possible scales of mapping. The words ‘certain degree’ mask the polythetic nature of areas of endemism. The polythetic characterization of areas of endemism implies that each locality of the study area has a large number of a set of species. Each species of this set is present in many of those localities and, generally, none of those species is present in every locality of the area. The converse will be a monothetic nature of areas of endemism where a taxon or group of taxa is present in all the localities of the study area. We propose here that the expansion of the definition of areas of endemism, including their polythetic characterization, will improve understanding of large biogeographic areas such as realms, regions, provinces, and districts, and will increase the scientific content (e.g., predictive capability and explanatory power) of areas of endemism.     

Biogeographic analysis of endemic cacti of the Sierra Madre Oriental, Mexico

The distribution of cacti species that inhabit the Sierra Madre Oriental (SMO) was analysed. Grid-cells were analysed using parsimony analysis of endemicity (PAE) and endemism indices. Areas characterized by their diagnostic species were determined, aiming to propose areas for the conservation of threatened cacti. Distributional data were obtained from 1936 herbarium specimens, electronic information, and from field collections. Eight areas of endemism and three main clades were obtained from the grid-cell analysis. Areas obtained from the endemism indices are very similar to those obtained with the PAE, but differ in the association of grid-cells. PAE showed endemism patterns indicating that southern and central sections of the SMO province are the areas richest in geographically-restricted species. The results obtained with different endemism indices detected more or less the same areas, although the importance level is different. The corrected weighted endemism index can be considered as a reliable measure of endemism because it is unrelated to species richness. A regionalization of the SMO in three subprovinces is suggested, supported by characteristic cacti taxa and the existence of natural barriers.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 373–389.     

Out of Amazonia again and again: episodic crossing of the Andes promotes diversification in a lowland forest flycatcher

Most Neotropical lowland forest taxa occur exclusively on one side of the Andes despite the availability of appropriate habitat on both sides. Almost all molecular phylogenies and phylogenetic analyses of species assemblages (i.e. area cladograms) have supported the hypothesis that Andean uplift during the Late Pliocene created a vicariant barrier affecting lowland lineages in the region. However, a few widespread plant and animal species occurring in lowland forests on both sides of the Andes challenge the generality of this hypothesis. To understand the role of the Andes in the history of such organisms, we reconstructed the phylogeographic history of a widespread Neotropical flycatcher (Mionectes oleagineus) in the context of the other four species in the genus. A molecular phylogeny based on nuclear and mitochondrial sequences unambiguously showed an early basal split between montane and lowland Mionectes. The phylogeographic reconstruction of lowland taxa revealed a complex history, with multiple cases in which geographically proximate populations do not represent sister lineages. Specifically, three populations of M. oleagineus west of the Andes do not comprise a monophyletic clade; instead, each represents an independent lineage with origins east of the Andes. Divergence time estimates suggest that at least two cross-Andean dispersal events post-date Andean uplift.     

Phylogeographic structure and mitochondrial DNA variation in true lemmings (Lemmus) from the Eurasian Arctic

The geographic pattern of mtDNA variation in lemmings from 13 localities throughout the Eurasian Arctic was studied by using eight restriction enzymes and sequencing of the cytochrome b region. These data are used to reveal the vicariant history of Lemmus , and to examine the effect of the last glaciation on mtDNA variation by comparing diversity in formerly glaciated areas to the diversity in non-glaciated areas. Phylogenetic congruence across different Arctic taxa and association between observed discontinuities, and probable Pleistocene barriers, suggest that glacial-interglacial periods were crucial in the vicariant history of Lemmus. Differences in amount of divergence (2.1–9.1%) across different historical barriers indicate chronologically separate vicariant events during the Quaternary. Populations from a formerly glaciated area are no less variable than those in the non-glaciated area. Regardless of glaciation history, no population structure and high haplotype diversity were found within geographic regions. The lack of population structure indicates that populations with high ancestral haplotype diversity shifted their distribution during the Holocene, and that lemmings tracked a changing environment during the Quaternary without reduction of effective population size.