Apetaenus (Apetaenus) litoralis Eaton

Subdivision of Apetaenus (Apetaenus) litoralis Eaton into subspecies

Eaton’s species is widely distributed in the subantarctic archipelagos, from Macquarie Island, south of New Zealand, to Marion Island, the westernmost island of the Kerguelen Biogeographical Province. After studying this species from various subantarctic sites, I have concluded that this species includes at least three distinct and easily recognizable geographical races, which are herein formally ranked at the subspecific level (see further).

Apetaenus litoralis is a flightless, micropterous fly strictly dependant on the nature of the soil microhabitats, like many other terricolous/lapidicolous arthropods, such as spiders and beetles. It is likely that some events of microspeciation can have taken place indeed in those organisms characterized by very scarce vagility, that is with a weak capability of dispersal, rather than in strongly flying insects which are influenced mainly by passive—e.g. storm winds—and active dispersal. Womersley (1937) recorded Apetaenus litoralis Eaton from Macquarie Island, the easternmost place in the distribution of this species known, at that time, only from the islands of the Kerguelen Province. Much later, Hardy (1962) stated that the specimens recorded by Womersley in his paper of 1937 belonged indeed to a new species, A. watsoni, described by Hardy himself in the same paper of 1962. Indeed both of these authors were right. The former had recognized in the examined specimens the peculiar morphological and chaetotactical traits which noticeably typify Eaton’s species, while the latter noticed that the individuals inhabiting Macquarie Island exhibited some consistent features that allowed separating them from the typical A. litoralis Eaton. After dissecting the male postabdomen of specimens of A. litoralis from Marion, Crozet, Kerguelen, and Macquarie islands, it was immediately clear to me that all of them belonged to the same species, although they were typified by such external characters that allowed subdividing them into three well differentiated subspecies, namely A. litoralis marionensis n. ssp., described herein from Marion Island, A. litoralis litoralis Eaton from the numerous other islands of the Kerguelen Biogeographical Province, and A. litoralis watsoni Hardy n. stat. from the easternmost Macquarie Island. On the other hand, it should be also stressed that Munari (2007) had already anticipated some doubts about the presumed validity of Hardy’s species.