Evolutionary geographic relationships among orthocladine chironomid midges from maritime Antarctic and sub‐Antarctic islands

Two species of chironomid midges are currently described in the genus Belgica Jacobs, 1900. Belgica antarctica Jacobs, 1900 is endemic to parts of the maritime Antarctic, and Belgica albipes (Séguy, 1965) is endemic to Îles Crozet, a sub‐Antarctic archipelago in the southern Indian Ocean. The relationships between these species, and their closest known relative (Eretmoptera murphyi Schaeffer, 1914, endemic to sub‐Antarctic South Georgia), were examined by sequencing DNA fragments for domains 1 and 3–5 of 28S ribosomal DNA and the mitochondrial gene cytochrome c oxidase 1 (cox1). The resulting molecular relationships between the three species were unclear, although their position within the subfamily Orthocladiinae of the Chironomidae, as generated by classical taxonomy, was confirmed. Our data reinforce earlier doubts, based on classical morphological approaches, that the generic placement of E. murphyi may be incorrect. Further analyses may indeed confirm that the species represents a third member of the genus Belgica. Genetic distance analysis, limited to the barcode region of cox1, indicated high differentiation between the two populations of B. albipes sampled (one obtained from the type location), suggesting the likely presence of cryptic species within this taxon, and that the taxonomic status of this species should be revised. Analysis of cox1 sequences in B. antarctica highlighted a strong genetic structure between populations obtained from 12 locations along the Antarctic Peninsula and the South Shetland Islands archipelago, with a number of distinctive mtDNA lineages inhabiting geographically distinct areas. In particular, we found four different haplogroups constituting geographically close but genetically distinct populations, a pattern likely to have been encouraged by the brachyptery of the members of this genus. We suggest that the different genetic patterns shown by each haplogroup have probably been determined by historical dispersal and colonization events during the Pleistocene, and are consistent with their survival in refuges in situ during successive glacial maxima over this period. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 258–274.     

Contrasting age structures in cave cricket populations: patterns and significance

Abstract.

• 1 Adaptation to life in caves, as a seasonally constant environment, is expected to affect several life history traits. In this paper we investigate the age structure and phenology of twenty-seven Dolichopodu cave cricket populations from artificial and natural caves subjected to different environmental regimes and to different availability of food resources.
• 2 Morphometric data clearly revealed the occurrence of different age structures and phenology, basically indicating two contrasting patterns.
• 3 In artificial caves, which have been colonized by Dolichopoda only in historical times and where food resources and climate are chiefly dependent upon surface environment, age structure was seasonal. In contrast, in most natural caves, where cricket colonization appears to be much older and stability of both climatic parameters and trophic resources is higher, age structure was diverse and aseasonal.
• 4 However, a seasonal age structure also occurs in natural caves characterized by either recent origin or by a low temperature regime. This suggests that age structure in Dolichopoda is influenced by historical factors, stability of food resources and also by environmental stress.