Gerromorpha (STYS & KERZHNER, 1975)

Damgaard, Jakob, 2008, Evolution of the semi-aquatic bugs (Hemiptera: Heteroptera: Gerromorpha) with a re-interpretation of the fossil record, Acta Entomologica Musei Nationalis Pragae 48 (2), pp. 251-268 : 257

Phylogeny of Gerromorpha

Living on a water surface enforces some strong ecological, physiological and behavioural constraints ( ANDERSEN 1982, SPENCE & ANDERSEN 1994). The comparison of the fossil Limnoporus wilsoni with extant congeners was used by to infer a ‘structural stasis’ in the group because the general habitus of fossil and extant specimens was practically inseparable ANDERSEN et al. (1993: Fig. 2). On the other hand, the adaptive shifts in habitats, for which gerromorphan bugs are so renowned, have ensured a rapid evolution of characters associated with locomotion, mating, feeding, and anti-predation strategies ( ANDERSEN 1982, SPENCE & ANDERSEN 1994). The many constraints associated with life history adaptations in Gerromorpha have lead to numerous autapomorphies and convergences in morphological characters, which have complicated the interpretation of these traits in a phylogenetic context. The waterstriders have long been preferred organisms for comparisons of morphological and molecular characters in simultaneous analyses in order to make a reciprocal illumination of the molecular and morphological evidence. Most studies have addressed the three principal Holarctic water strider genera: Limnoporus Stål, 1868 , Aquarius Schellenberg, 1800 and Gerris Fabricius, 1794 ( DAMGAARD & COGNATO 2003, 2005), but also sea skaters ( Halobates Eschscholtz, 1822 ) have been studied ( DAMGAARD et al. 2000). Along with these investigations of more shallow relationships, a few studies have addressed relationships among families and subfamilies by including DNA sequence data ( MURAJI & TACHIKAWA 2000, DAMGAARD et al. 2005). So far, DAMGAARD (in press) has presented the most inclusive study in terms of taxon and character sampling. A few subfamilies, such as Madeoveliinae ( Mesoveliidae ), Hyrcaninae ( Hebridae ), Heterocleptinae and Limnobatodinae (both in Hydrometridae ) still await inclusion, and will be very important for understanding the basal divergences of the infraorder.

Figure 1 shows recognized gerromorphan fossils optimized onto the most parsimonious tree resulting from a simultaneous parsimony analysis of molecular and morphological characters by DAMGAARD (in press). The fossil gerrid subfamily Electrobatinae and Cretogerris albianus , which has not been assigned to any subfamily, are placed unresolved at the base of the Gerridae , and the two extant hydrometrid subfamilies, Heterocleptinae and Limnobatodinae , are placed according to ANDERSEN (1982).

Figures

Fig. 1. Phylogenetic tree for the families of Gerromorpha and subfamilies of Hydrometridae, Veliidae and Gerridae summarized from DAMGAARD (in press). Temporal distribution of fossils indicated by heavy branches; unbroken branches denote range extensions inferred from fossils; broken branches denote range extension inferred from sister group relationships.