Towards reliable detection of introgression in the presence of among-species rate variation.

The role of interspecific hybridization has recently seen increasing attention, especially in the context of diversification dynamics. Genomic research has now made it abundantly clear that both hybridization and introgression - the exchange of genetic material through hybridization and backcrossing - are far more common than previously thought. Besides cases of ongoing or recent genetic exchange between taxa, an increasing number of studies report "ancient introgression" - referring to results of hybridization that took place in the distant past. However, it is not clear whether commonly used methods for the detection of introgression are applicable to such old systems, given that most of these methods were originally developed for analyses at the level of populations and recently diverged species, affected by recent or ongoing genetic exchange. In particular, the assumption of constant evolutionary rates, which is implicit in many commonly used approaches, is more likely to be violated as evolutionary divergence increases. To test the limitations of introgression detection methods when being applied to old systems, we simulated thousands of genomic datasets under a wide range of settings, with varying degrees of among-species rate variation and introgression. Using these simulated datasets, we showed that some commonly applied statistical methods, including the D-statistic and certain tests based on sets of local phylogenetic trees, can produce false-positive signals of introgression between divergent taxa that have different rates of evolution. These misleading signals are caused by the presence of homoplasies occurring at different rates in different lineages. To distinguish between the patterns caused by rate variation and genuine introgression, we developed a new test that is based on the expected clustering of introgressed sites along the genome, and implemented this test in the program Dsuite.

A new species of Trachylepis (Squamata: Scincidae) from the Amhara Region, Ethiopia, and a key to the Ethiopian Trachylepis.

Ethiopia is known for its highly endemic and rich herpetofaunal diversity shaped by its biogeographical patterns. Here, a new species of skink, Trachylepis boehmei sp. nov., is described from the Ethiopian Highlands. It differs from its congeners in having smooth uncarinated dorsal scales, 26-29 scale rows around midbody, a slender body of small size, a relatively short tail, a low eye-snout distance and a unique colour pattern with 6-8 darkish brown dorsal stripes. Based on morphological characteristics, its biogeographical pattern and comparisons with other similar congeners this new species is closely related to Trachylepis megalura. A published new record of Trachylepis wingati for the Kafa region is re-examined and identified as T. megalura. An updated comprehensive key to the Trachylepis found in Ethiopia is provided. In the context of ongoing phylogenetic and taxonomic revisions of Trachylepis and its species complexes the presence of further cryptic taxa can be expected also for the Ethiopian biodiversity hotspots. Consequently, the need of further herpetological investigations in this region of ecological importance is stressed.

A new species of Dibamus Duméril Bibron, 1839 (Squamata: Dibamidae) from Pulau Manado Tua, Northern Sulawesi, Indonesia.

Based on three adult specimens, viz. two males and a female that form the type series, a new species of blind or worm-like lizards is described from Pulau (= Island) Manado Tua, a little volcanic island located off the northern tip of the Minahassa Peninsula of Sulawesi, Indonesia. Dibamus manadotuaensis sp. nov. differs from all congeneric species in the following unique combination of characters: maximum snout-vent length 135 mm; tail length up to 14.2 mm (i.e., 12-13% of SVL); labial and nasal sutures present and complete; four (three) postoculars; four to six scales on posterior edge of infralabial; 26-28 midbody scale rows; 30-33 transverse scale rows posterior to head; 25 transverse scale rows anterior to vent; 218-232 ventral scales; 39 subcaudal scales; relative size of frontal to frontonasal 0.68-0.73; relative size of interparietal to surrounding scales 0.67-1.43; 132-135 presacral and 21-24 postsacral vertebrae. Morphologically, D. manadotuaensis is most similar to D. celebensis, which occurs on mainland Sulawesi.Dibamus manadotuaensis sp. nov. represents the twenty-fourth species of Dibamus and the third species of this genus recorded from the Sulawesi region. At the same time, it is the only squamate species considered endemic for the islands of the Bunaken Marine National Park, to which Manado Tua belongs.