Taxonomy of the rear-edge populations: the case of genus Anterastes (Orthoptera, Tettigoniidae)

Abstract

The stabilized and the trailing edge glacial relicts are candidate model organisms to be used to link taxonomy to phylogeography. We attempted to establish such a link by considering the taxonomy and phylogeography of the genus Anterastes, consisting of glacial relict taxa/populations. Species delimitation tests indicated 13–22 candidate species in the genus. Analyses suggested inversely related genetic and phenotypic divergence. By integrating these results, we reached the following conclusions. (i) The plausible taxonomical composition is recognizing 16 species in the genus; of these three are new, A. kizkayasiensis sp. n., A. muratdagensis sp. n., and A. boreoanatoliensis sp. n., and the last two are cryptic. (ii) Generic radiation corresponds to three stages as Pliocene, Pleistocene prior to mid-Pleistocene Transition (MPT), and post-MPT. The ultimate ancestor of two species, corresponds to the first and of other 14 to the second and proximate ancestor of all species to the third period. These ages suggest that the pre-MPT ancestors are stabilized edge while those of post-MPT are trailing edge populations. (iii) Since members of the genus demand cold habitats, the isolated relict ancestors on highlands evolved under similar selection pressures, and this led to a conserved phenotype, consequently to cryptic or morphologically poorly diverged species, as genetic data indicate each constitutes a reproductively isolated distinct phylogenetic unit. (iv) Although morphological diagnosability is poor, each species fulfills criteria of several species concepts and can be differentiated by clear allopatric range, providing one of five criteria assumed by Darwin for species delimitation.

Appendix 1. Descriptions of three new species given in the study

Genus Anterastes (Brunner von Wattenwyl, 1882)

Anterastes kizkayasiensis Çıplak & Uluar sp.n.

(Fig. 5).

LSID urn:lsid:zoobank.org:act:BF085BEB-AFE3-4965–9752-07B12DB3D0C6.

Holotype, ♂, TURKEY: Konya, Kızkayası Mt., 38° 05′ 019.7″ N, 32°16′ 056.0″ E, 1644 m, 01.07.2008 (Çıplak et al.) (MEVBIL).

Paratypes, 7♂, 9♀, same data as holotype.

Diagnosis: As stated by genetic data, the new species constitutes an independent phylogenetic and reproductive unit within A. babadaghi group (given as A. cf. ucari in Çıplak et al., 2015). It can be differentiated from other members of the group by the allopatric species range distribution. The new species share morphological features of A. babadaghi group (see Çıplak, 2004), but more similar to A. ucari and A. babadaghi. Although differences are not prominent, it is not a cryptic species and can be distinguished from these two by a smaller size and especially short, slender, and almost straight ovipositor and narrower incision of the female subgenital plate. The PCA applied to 23 metric characters well distinguish it from other members of the species group (Fig. 4). In addition to phenotype, the ML tree obtained from full data set subjected to PAUP analysis defined the following unique base changes for the new species; 248 (A- > G), 683 (T- > C), 692 (A- > C) and 1268 (A- > G). The lists of the unique and non-unique base changes is presented in Fig. 2 and File S1.

Etymology. The species was named after the type locality, the Kızkayası Mt. in Konya provinces of Turkey.

Fig. 5

Morphologic structures of Anterastes kizkayasiensis sp. n.: A pronotum + tegmina from above and profile, B male anal tergum and cerci, C titillators, D female subgenital plate, E ovipositor [diagnostic structures (female subgenital plate and ovipositor) of sister species Anterastes ucari are given in the box for the comparison.]

Anterastes boreoanatoliensis Çıplak & Uluar sp.n.

(Fig. 6).

LSID urn:lsid:zoobank.org:act:98C005E3-DDED-4C45-B51F-BE4122C4890E.

Holotype, ♂, TURKEY: Giresun, Şebinkarahisar, 40° 27′ 046.2″ N 38° 42′ 048.3″ E, 2294 m, 22.07.2005 (Çıplak et al.) (MEVBIL).

Paratypes, 45♂, 40♀, same data as holotype; 18♂, 29♀, Sivas, Kösedağ Mt., 40° 09,029.7″ N, 37° 51′ 002.6″ E, 1802 m, 23.07.2009 (Çıplak et al.); 13♂, 5♀, Kastamonu, Ilgaz Mt., 41° 03′ 024.3″ N, 33° 43′ 005.8″ E, 2045 m, 13.08.2004 (Çıplak et al.); 11♂, 29♀, Çankırı, Çerkes, Işık Mt., 40° 41′ 027.8″ N 32° 44′ 006.4″ E, 1595 m, 22.06.08 (Çıplak); 2♂, Erzincan, Pöske Mt., 39° 53′ 26.4′′ N, 39° 21′ 43.3′′ E, 2169 m, 19.07.2016 (Çıplak & Kaya) (MEVBIL).

Diagnosis: The new species exhibits morphological features of A. serbicus group (given as A. cf. serbicus in Çıplak et al., 2015). It is morphologically cryptic and cannot be diagnosed from other members of the group. Especially, it is similar to A. serbicus and A. antitauricus by the titillators without curved apical arms. However, genetic data suggest it as a well-supported independent phylogenetic unit. It can be properly diagnosed from other members of the group by its allopatric range. Although this new species occurs as sympatric with A. niger in Sivas, each belongs to different species groups. The ML tree of full molecular data displayed following unique base changes for the new species; 21 (A- > G), 205 (A- > G), 626 (C- > T), 627 (C- > T) 653 (T- > A), 662 (T- > G), and 1160 (A- > T) (see Fig. 2 and File S1).

Etymology: Range of this new species covers western and northern Black Sea Basin or boreal part of Anatolia and the species name was established after this eco-geographic feature of the species’ range.

Fig. 6

Morphologic structures of Anterastes boreoanatoliensis sp. n.: A pronotum + tegmina from above and profile, B male anal tergum and cerci, C titillators, D female subgenital plate, E ovipositor [diagnostic structures (female subgenital plate and ovipositor) of sister species Anterastes serbicus are given in the box for the comparison.]

Anterastes muratdagensis Çıplak & Uluar sp.n.

(Fig. 7).

LSID urn:lsid:zoobank.org:act:682441CF-FFDF-48BC-B32D-629070BFA231.

Holotype, ♂, TURKEY: Uşak, Murat Mt., 38° 56′ 054.7″ N, 29° 37′ 029.4″ E, 1785 m, 17.07.2009 (Çıplak et al.) (MEVBIL).

Paratypes, 16♂, 21♀, same data as holotype.

Diagnosis: The new species exhibits morphological features of A. burri especially by the apically bent apical arms of titillators, and also general characteristics of A. serbicus group (given as A. cf. burri in Çıplak et al., 2015). It can poorly be distinguished from other members of the group by pronotum (the length, width, and length/width of the pronotal disk in male and female). Genetic data suggest it as an independent phylogenetic and reproductive unit. Although it cannot be diagnosed by morphology, it can be well diagnosed from other members of the group by its range allopatric to all other members of the genus. The new species has the following unique base changes in the ML tree of full data set; 25 (A- > T), 284 (A- > G), 335 (G- > T), 569 (A- > T), 653 (T- > A), 770 (A- > C), 1076 (A- > C), 1157 (C- > T), 1394 (C- > T), and 1565 (T- > C) (see Fig. 2 and File S1).

Etymology: The species was named after the type locality of the species, the Murat Dağ Mt. in Uşak province in Aegean Basin of Turkey.

Fig. 7

Morphologic structures of Anterastes muratdagensis sp. n.: A pronotum + tegmina from above and profile, B male anal tergum and cerci, C titillators, D female subgenital plate, E ovipositor (diagnostic structures [female subgenital plate and ovipositor) of sister species Anterastes burri are given in the box for the comparison.]