CONICET | Buscador de Institutos y Recursos Humanos

The Hydroporinae tribe Vatellini is conformed by four genera of small- to medium-sized aquatic beetles. One of these is the Neotropical genus Macrovatellus Sharp, with one species, M. haagi, occurring in Argentina. The phylogenetic relationships among tribes within Hydroporinae are unclear. This subfamily is presently subdivided into nine tribes (Laccornini, Methlini, Hydroporini, Hygrotini, Bidessini, Hydrovatini, Carabhydrini, Hyphydrini and Vatellini), for many of which there is evidence of monophyly coming from adults and/or larvae. However, a hypothesis on the relationships of Vatellini with other members of the subfamily was not clearly presented. Larval morphology of the Vatellini is poorly known, and no studies have still included detailed larval descriptions of members of this tribe. Therefore, the weak phylogenetic hypotheses on its relationships based on adult characters have not been revised considering other character systems. Modern works on larval Dytiscidae have focused on a more exhaustive analysis of the chaetotaxy and porotaxy. The implementation of the system of nomenclature of larval chaetotaxy and porotaxy previously developed for the subfamily Hydroporinae, combined with a detailed analysis of the morphometric relationships among different structures of the larvae, provides a useful basis to determine characters that enable to establish phylogenetic relationships among the taxa. Our goal was to present a preliminary study of the phylogenetic relationships of the tribe Vatellini within Hydroporinae based on larval characters, for which the three larval instars of Macrovatellus haagi (Wehncke) were described and figured. Primary and secondary setae and pores were distinguished in the head capsule, head appendages, legs, last abdominal segment and urogomphi. For parsimony analysis, 46 binary and 11 multistate characters (treated as unordered) were coded for 18 taxa including M. haagi and representatives of five other tribes of the Hydroporinae. Previous papers have suggested that the genus Laccornis Gozis represents the sister group of remaining Hydroporinae; for this reason, larvae of this genus were considered as an outgroup. The data matrix was analyzed using the program TNT. The small size of the matrix allowed for the implementation of an exact solution algorithm (implicit enumeration). Branch support was calculated by jackknifing (P = 36, 200 replicates). The 82-step single most parsimonious cladogram obtained has the following structure: (Laccornis ((Hydroporini Hygrotini) (Liodessus (Macrovatellus haagi (Pachydrus (Microdytes (Hyphydrus Desmopachria))))))). Jackknife values between 83-100 indicate that all clades are well supported. Many of the characters included in the data matrix resulted uninformative (autapomorphies). Since the exclusion of these characters from the analysis produces no changes in topology, they were retained. Some characters were coded ambiguously for the taxa Hydroporini and Hygrotini since different states are present in the genera of these tribes. To eliminate ambiguities, a preliminary analysis was conducted including all genera of Hydroporini and Hygrotini as terminals. In this case, several most parsimonious cladograms were obtained, for which the strict consensus was calculated. The consensus cladogram showed a basal polytomy including many Hydroporini genera, Hygrotini and the clade composed by Liodessus Guignot (Bidessini), M. haagi and Hyphydrini. As the relationships within this last clade are not affected by the inclusion of a terminal for each genus of Hydroporini and Hygrotini, we treated these two tribes as terminals in our analysis. The results support the hypothesis of a derived condition of the tribe Vatellini within Hydroporinae. The clade Liodessus + M. haagi + Hyphydrini and the clade M. haagi + Hyphydrini are supported by three and four synapomorphies, respectively. Several autapomorphies of M. haagi strongly suggest a monophyletic origin of the tribe Vatellini.

enviar mensaje