Dissertationen online der Freien Universität Berlin


Phylogeny and zoogeography of the Sericini in the Himalayan region
Ahrens, Dirk

HaupttitelPhylogeny and zoogeography of the Sericini in the Himalayan region
Titelzusatz(Insecta: Coleoptera: Scarabaeidae)
TitelvariantePhylogenie und Zoogeographie der Sericini des Himalaya-Gebietes
Zusatz zur Titelvariante(Insecta: Coleoptera: Scarabaeidae)
AutorAhrens, Dirk
Geburtsort: Neubrandenburg/ BRD
GutachterProf. Dr. Walter Sudhaus
weitere GutachterProf. Dr. Holger Dathe
Freie Schlagwörterscarab beetles, Himalaya, cladistic analysis, morphology, biodiversity
DDC570 Biowissenschaften; Biologie
Zusammenfassung1) To determine the phylogenetic position of the Sericini (Coleoptera: Scarabaeidae), cladistic analyses were performed. The taxa included in the analysis represent most the "traditional" subfamilies of coprophagous and phytophagous Scarabaeidae, with emphasis on the Sericini and melolonthine lineages. Several poorly studied exoskeletal features have been examined including the elytral base, posterior wing venation, mouth parts, endosternites, coxal articulation, and genitalia. The results of the analysis strongly support the monophyly of the "orphnine group" + "melolonthine group". This clade was identified as the sister group to the "aphodiine line" including Aphodius + Copris. The "melolonthine group" is comprised in the strict consensus tree by two major clades, with the included taxa of Euchirinae, Rutelinae, and Dynastinae nested together in one of the clades ("melolonthine group I"). Melolonthini, Cetoniinae, and Rutelinae are strongly supported as being monophyletic, while Melolonthinae and Pachydemini appear as paraphyletic. Sericini + Ablaberini were identified in the analysis to be sister taxa nested within the "melolonthine group II" clade. As this clade is distributed primarily in the southern continents, one could assume that Sericini + Ablaberini are derived from one of these southern lineages. It is plausible that the ancestors of Sericini + Ablaberini and Athlia were separated by a vicariance event, such as the separation of the African plate from the rest of Gondwana, while Sericini and Ablaberini likely diversified during early Tertiary, with dispersal of some basal Sericini to South America. 2) The Sericini constitute a monophyletic group based on the following apomorphies: (1) vestigial (9th) sternite in the spiculum gastrale absent; (2) cranial process of the spiculum gastrale filiform, very slender and circular in cross section; (3) glandulae accessoriae with left and right glandulae (1+2) having a common duct to the vagina; (4) basal ostium of phallobase small; and (5) metacoxa enlarged. 3) To explore the diversification patterns of Sericini in the Himalaya, eight monophyletic groups have been analysed using cladistics, including Anomalophylla, Calloserica, Lasioserica/ Amiserica, Maladera (subgenus Omaladera), Maladera (subgenus Cycloserica), Serica, Sericania, and Xenoserica gen. n./ Nipponoserica. The Himalayan region has been treated as unit embracing the complex system of nearly parallel mountain ranges, from North Burma in the east to nearly Afghanistan in the west (approximately between 72° and 91° E and 27° and 36°N). 4) All Himalayan sericine taxa belong to a distal sericine lineage ("modern" Sericini), sharing the following apomorphic characters states: the presence of a carina from the craniolateral margin of the mesosternum to the mesofurcal arm and the acutely bent anterior anal vein (AA). 5) The phylogenies found show a congruent pattern in groups with similar vertical and/or horizontal distribution. Patterns of vertical and/or horizontal distribution are shown to be of crucial importance for gene flow, dispersal capacity, and for the opportunity to occupy new habitats. In lower montane species, major distal clades are generally restricted to the Himalaya, as revealed in Omaladera or Lasioserica. Among the montane lineages, the following general pattern of diversification have been hypothesized: (A) Himalayan xerophilous forms, such as Sericania, are supposed to have evolved also in the northern and drier parts of Tibet; this corridor should have been responsible for their interference with areas of north-eastern Asia. With progressing uplift and aridization of northern Tibet, and strengthened monsoon, the basal lineages of Sericania have been separated into a North-West Himalayan and East Asian clade. (B) Multiple events of radiation in Himalayan Sericini along southern slope of Himalaya regarding taxa of the more humid areas of the Himalayan southern slope, such as in Calloserica, Omaladera, or Lasioserica. This hypothesis is mainly supported by the congruent cumulative ranges of certain distal clades of species. The fact, that a great number of diverse sericine groups performed a strong diversification within these mountain chains, lead to assume that the presence of mountain ranges with the characteristics similar to the present Himalaya predate those diversification processes. Similar patterns result from preliminary cladistic analyses of Microserica, Nepaloserica, and Oxyserica. (C) Major distal clades of middle to upper montane species show a stronger interference with the mountain regions of eastern Tibet as apparent from cladistic analysis of Serica. This would implicate that flight-active organisms of medium and upper montane belt had in present and/or past better opportunities for dispersal along and across higher mountain chains as encountered in the Himalaya or eastern Tibet. (D) Diversification at eastern margin of Tibetan Highland, with (rather recent) range extension north-easterly and westerly (Anomalophylla). (E) Most of the forms occurring in lowland and in the colline regions of the Himalaya represent taxa with extensive ranges having here a limit of their distribution. To these belong the taxa with range belonging for example to Himalayan-Indochinese or to Himalayan-Indian chorotype. Among the forms of the lowland areas, only a very few developed monophyletic Himalayan lineages, such as the taxa belonging to the Maladera (subgenus Cycloserica). For this group results of cladistic analysis reveal a separating effect of the Himalayan-Alpine belt. It is postulated that two Cycloserica lineages existed before they dispersed into the two separated areas, the northern Indian subcontinent (Himalaya) and the Middle Asian lowland. 6) The occurrence of numerous basal lineages in the Himalaya, additionally, lead to assume that the Himalaya was in historical framework also a "refugium", being able to buffer fluctuations of climate by "orobiom-shifting". These "refugia" might be related also to special topographical structures such as large river valleys which were able to cross the Great Himalayan chain, as apparent in case of Xenoserica. In the Himalaya presently very restrictedly occurring basal lineages of e. g. Lasioserica or Serica should be interpreted as relics of former widely distributed clades. The taxa of these clades became extinct in great part, probably also in consequence of competition of the strongly radiating younger lineages. 7) There is comparatively high evidence from range positions of closely related species for allopatric geographical speciation in Lasioserica with the majority of closely related Central Himalayan species occurring allopatrically or parapatrically. However, in the more easterly distributed lineages, this pattern is altered by the contrary, with a great portion of closely related species occurring sympatrically. This differentiated pattern might be attributed to the climatic gradient in present and past which has been characterizing this mountain range at least since onset of monsoon climate with its humid south-eastern summer winds. 8) About 60 % of the Himalayan fauna is composed by locally endemic species. Comparative biogeographical analyses (species similarity, parsimony analysis of endemism) and species' phylogeny reveal evidence to hypothesize two principal centres of endemism in the Himalaya: a north-western centre and a south-eastern centre. 9) Beside numerous newly discovered species, the cladistic analyses result in the following preliminary taxonomic conclusions: Cycloserica Reitter, 1896 (= Leucoserica Reitter, 1896 syn. n.); Maladera (Cycloserica) arenicola (Solsky, 1876) comb. n.; Nipponoserica Nomura, 1972 (= Pseudosericania Kobayashi, 1980 syn. n.), Amiserica antennalis (Nomura, 1974) comb. n., Xenoserica gen. n., Xenoserica sindhensis (Ahrens, 2000) comb. n., X. pindarensis (Ahrens, 2000) comb. n.
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Fachbereich/EinrichtungFB Biologie, Chemie, Pharmazie
Tag der Disputation01.11.2004
Erstellt am25.11.2004 - 00:00:00
Letzte Änderung19.02.2010 - 14:28:24
Alte Darwin URLhttp://www.diss.fu-berlin.de/2004/305/
Statische URLhttp://www.diss.fu-berlin.de/diss/receive/FUDISS_thesis_000000001385