Temperature niche difference and interspecific competition determine the parapatric distribution of two congeneric species in Diaphanosoma

Background Diaphanosoma excisum and D. dubium are parapatrically distributed in tropical and subtropical waters, and rarely coexist at local communities in the transition between tropics and subtropics. According to Janzen’s hypothesis and the modern coexistence theory, the specific thermal adaptation and strong interspecific competition between the two congeneric species are assumed to result in their range limits. To explore the mechanisms underlying such parapatric distribution, we modeled their current geographic distribution, and compared temperature niche difference and fitness inequality in interspecific competition with their representative clones.Results The species distribution modeling showed that the two Diaphanosoma species had significantly divergent climate niches. Their life history parameters in monocultures also demonstrated as stable temperature niche difference, while D. excisum had higher fitness than D. dubium in dimension of food niche. The competition experiments revealed a strong exploitative competition between the two species, and D. excisum was the superior competitor, and excluded D. dubium in all the competition experiments within overlapping temperature niche regardless of food conditions.Conclusions Our results suggest that stable temperature niche difference overcoming interspecific competition for food plays a critical role in shaping Diaphanosoma species range.

Revision of the Baeoglena species of the West Palaearctic Region (Coleoptera: Staphylinidae: Aleocharinae)

The subgenus Baeoglena Thomson, 1867 of the speciose aleocharine genus Oxypoda Mannerheim, 1830 has been subject to considerable taxonomic confusion rendering a reliable identification of material from regions other than Central Europe and the Canary Islands virtually impossible. Based on a revision of abundant material from various major public and private collections, seven species are distributed in the West Palaearctic region exclusive of the Canary Islands. Two new species are described and illustrated: Oxypoda (Baeoglena) rectacia spec. nov. (East Mediterranean, from South Greece to the Middle East) and O. (B.) derecta spec. nov. (West Caucasus, Northeast Anatolia). Diagnoses and illustrations of the genitalia are provided for the remaining five species. The following synonymies are established: Oxypoda nova Bernhauer, 1902 = O. giachinoi Pace, 2001, syn. nov.; O. hispanica Fagel, 1958 and its replacement name O. inexpectata Fagel, 1965 are removed from synonymy with O. praecox Erichson, 1839 and synonymized with O. fusina Mulsant & Rey, 1875. Oxypoda recondita Kraatz, 1856 and O. dalmatina Bernhauer, 1905 are excluded from Baeoglena and moved to the subgenus Bessopora Thomson, 1859. Lectotypes are designated for Oxypoda nova Bernhauer, 1902, O. caucasica Bernhauer, 1902, and O. kuehnelti Scheerpeltz, 1963. An outline of the taxonomic history, a diagnosis of the subgenus, a checklist, and a key to species are provided. A zoogeographic analysis revealed some remarkably discontinuous distributions and parapatric distribution patterns which are plausibly explained only with interspecific competition among Baeoglena species. The distributions of the subgenus as a whole and of the individual species in the West Palaearctic region are mapped. Taxonomic acts Oxypoda rectacia spec. nov. – urn:lsid:zoobank.org:act:8E5A6F28-9AD3-474E-99F8-9CBA0F85C4DC Oxypoda derecta spec. nov. – urn:lsid:zoobank.org:act:4C73E05F-20F7-4697-A4BA-D9E030B28A27

Polyploidy and genome size variation in Phlox nana (Polemoniaceae) from the Pecos plains of New Mexico and the Davis Mountains of West Texas

Polyploidy is conspicuous in the genus Phlox, and some species exhibit variation in ploidy levels, or cytotypic variation. Diploid, tetraploid and hexaploid popula-tions of P. nana occur across parts of the species distribution in the southwestern United States and northern Mexico. A recent study highlighted two areas for which ploidy level inferences were challenging: a population on the Pecos Plains of New Mexico (“Caprock”) and the Davis Mountains region of West Texas. Plants in these areas were sampled and chromosome counts and flow cytometry methods were used to assess ploidy levels and genome sizes. Homoploid variation in ge-nome size was unambiguously documented: the genome size of tetraploid plants from the Davis Mountains was significantly larger than that of plants from Caprock. The general condition of larger genome sizes for plants in the Davis Mountains explains previous difficulty in determining ploidy levels within the region. Most plants at the Caprock population appeared to be tetraploid (2n=28), but chromosome counts revealed variants, including some putative pentaploids. Within the Davis Mountains region, both diploid (2n=14) and tetraploid (2n=28) cytotypes were documented, with a parapatric distribution. Overall, this study clarifies patterns of cytotypic diversity in P. nana, highlights an example of infraspecific, homoploid genome size variation, and contributes to a framework for ongoing evolutionary investigation in this study system.

Phylogenetic diversity within the endemic brown trout Duero lineage: implications for conservation and management

Brown trout display great phenotypic and genetic variability. Use of mitochondrial DNA (mtDNA) variation has allowed the definition of seven different lineages in this species to date. One of them, the Duero (DU) lineage, was initially detected in the inner section of the Duero River in Spain, where it showed a parapatric distribution with the more widely distributed Atlantic (AT) lineage. Later mtDNA-RFLP (restriction fragment length polymorphism) studies detected the DU lineage in northern Spanish basins (Galicia). The aim of this work was to ascertain the origin and variability of these DU populations outside the Duero drainage. Using complete mtDNA control region sequencing, 11 novel DU haplotypes were identified. Several of them could be assigned to an endemic group in Galicia consistent with the long-time presence of the DU lineage outside the Duero River, and excluding a recent origin by human translocations. The DU haplotype group observed in north-western Iberian basins was estimated to diverge from that of the Duero River more than 100000 years ago. We therefore advocate for conservation strategies at regional and local scales rather than focussed in a single ESU as proposed in earlier works.

Mitochondrial diversity of the widespread Central Asian steppe tortoise (Testudo horsfieldii Gray, 1844): implications for taxonomy and relocation of confiscated tortoises

Using a nearly range-wide sampling, we investigated phylogeographic differentiation and mitochondrial diversity of Testudo horsfieldii, the only tortoise species confined to Central Asia. We identified three major haplotype clades with mainly parapatric distribution that do not correspond well to the currently recognized three subspecies. One clade is restricted to the Fergana Valley and seems to represent a previously overlooked evolutionarily significant unit. Another clade, consisting of several largely parapatrically distributed haplotypes, occurs in the north and the central southern part of the species' range. The third clade, likewise comprising several largely parapatrically distributed haplotypes, was identified from the south-eastern corner of the Caspian Sea in the west, from Afghanistan and Pakistan in the east and from two more northerly sites in western and south-eastern Uzbekistan. It is possible that this clade also occurs in eastern Turkmenistan and adjacent Afghanistan, regions not sampled for the present study. The generally parapatric distribution of individual haplotypes, even within each of the three major clades, suggests advanced lineage sorting, either due to limited dispersal abilities, glacial isolation in distinct local microrefuges or both acting in accord. The localized distribution of endemic haplotypes in the northern and central plains as well as in the mountainous eastern and southern parts of the distribution range supports the existence of multiple microrefuges there. Records of haplotypes of distinct clades in sympatry or close geographic proximity are likely the result of Holocene range expansions. In recent years, thousands of confiscated steppe tortoises were released into the wild. The detected mitochondrial differentiation offers a powerful tool for nature conservation, as a means of determining the geographic origin of confiscated tortoises and selecting suitable reintroduction regions.