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Phylogenetic Species Concept (phylogenetic + species_concept)
Selected AbstractsThe implications of different species concepts for describing biodiversity patterns and assessing conservation needs for African birdsECOGRAPHY, Issue 5 2005Shaun Dillon It has been suggested that switching from the widely used Biological Species Concept to a Phylogenetic Species Concept, would result in the appearance of hitherto neglected patterns of endemism. The problem has mainly been analyzed with respect to endemic taxa and for rather limited geographical regions, but will here be analysed for the entire resident avifauna of sub-Saharan Africa. A database of African bird distributions was re-edited to create two new datasets representing 1572 biological species and 2098 phylogenetic species. Species richness patterns were virtually identical with the two taxonomies, and only subtle changes were found in the geographical variation in range-size rarity sum. However, there were some differences in the most range-restricted species, with increased complexity of long-recognized centres of endemism. Overall, then, the large-scale biogeographic patterns are robust to changes in species concepts. This reflects the aggregated nature of endemism, with certain areas acting as "species pumps" and large intervening areas being characterised by a predominance of widespread species which distribute themselves in accordance with contemporary environmental conditions. The percentages of phylogenetic and threatened species captured in a BSC near-minimum set of 64 grid-cells and a PSC near-maximum set, with the same number of grid-cells, are very similar. [source] World-wide genetic differentiation of Eubalaena: questioning the number of right whale speciesMOLECULAR ECOLOGY, Issue 11 2000H. C. Rosenbaum Abstract Few studies have examined systematic relationships of right whales (Eubalaena spp.) since the original species descriptions, even though they are one of the most endangered large whales. Little morphological evidence exists to support the current species designations for Eubalaena glacialis in the northern hemisphere and E. australis in the southern hemisphere. Differences in migratory behaviour or antitropical distribution between right whales in each hemisphere are considered a barrier to gene flow and maintain the current species distinctions and geographical populations. However, these distinctions between populations have remained controversial and no study has included an analysis of all right whales from the three major ocean basins. To address issues of genetic differentiation and relationships among right whales, we have compiled a database of mitochondrial DNA control region sequences from right whales representing populations in all three ocean basins that consist of: western North Atlantic E. glacialis, multiple geographically distributed populations of E. australis and the first molecular analysis of historical and recent samples of E. glacialis from the western and eastern North Pacific Ocean. Diagnostic characters, as well as phylogenetic and phylogeographic analyses, support the possibility that three distinct maternal lineages exist in right whales, with North Pacific E. glacialis being more closely related to E. australis than to North Atlantic E. glacialis. Our genetic results provide unequivocal character support for the two usually recognized species and a third distinct genetic lineage in the North Pacific under the Phylogenetic Species Concept, as well as levels of genetic diversity among right whales world-wide. [source] Phylogenetic Species, Nested Hierarchies, and Character FixationCLADISTICS, Issue 4 2000Paul Z. Goldstein Cladistic mechanics and ramifications of various species concepts rooted in phylogenetic theory are explored. Published discussions of the phylogenetic species concept (PSC) have been hampered by persistent misconceptions surrounding its ontology and applicability, and by confusion of various incompatible versions of species concepts claiming to follow from Hennig's (1966), Phylogenetic Systematics, Univ. of Illinois Press, Urbana work. Especially problematic are topology- or tree-based versions of species diagnosis, which render diagnoses dependent on relationships depicted as hierarchically structured regardless of any lack of underlying hierarchy. Because the applicability of concepts such as monophyly, paraphyly, and polyphyly rests ultimately on the underlying hierarchical distribution of characters, representations of tokogenetic or reticulating systems as nested hierarchies are necessarily inaccurate. And since hierarchical representations,even if accurate,of nonrecombining genetic elements need not coincide with the organisms that bear them, tree-based diagnoses are further hampered, except potentially as retrospective tools. The relationship between tree-based species delineations and the criterion of character fixation is explored. Fixation of characters by which one identifies phylogenetic species is further distinguished from the fixation of character state differences, and the implications of that distinction are explored with reference to the interpretation of speciation events. It is demonstrated that character fixation in alternative species need not coincide with the achievement of reciprocal monophyly. While the PSC retains shortcomings, some of the more frequently criticized aspects of the PSC are functions of sampling that are no more problematic than for any basic systematic endeavor. [source] Genetic and morphological evidence for reproductive isolation between sympatric populations of Galaxias (Teleostei: Galaxiidae) in South Island, New ZealandBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2001JONATHAN M. WATERS New Zealand's South Island houses a flock of closely related stream-resident fish taxa (Galaxias vulgaris sensu lato), including a number of species recently described on the basis of subtle morphological differences. The taxonomic status of some members of the species complex remains uncertain. This study examines the degree of reproductive isolation between recently recognized morphotypes from Southland (G. ,southern', flatheads; G. gollumoides, roundheads) which co-occur in Bushy Creek, a tributary of the Mataura R. Although these morphotypes are broadly sympatric in Southland and Stewart Island, Bushy Creek is their only documented zone of contact. Molecular (microsatellite, isozyme and mtDNA markers) and morphological analyses of 139 fish samples across a 500-m transect (seven stations) reveal a cline from predominantly G. ,southern' (N=85) to predominantly G. gollumoides (JV=54), corresponding with a gradual increase in stream gradient. Multivariate analyses of genotypic and morphological data independently reveal distinct clusters that are completely congruent with mtDNA type, suggesting an absence of mtDNA introgression. Our data support the separate species status of G. ,southern' and G. gollumoides under both biological and phylogenetic species concepts. We suggest that the speciation of these taxa occurred in allopatry through independent losses of diadromy, with sympatry resulting from secondary contact. [source] | ||||||||||