The aquatic leaf beetle speciesMacroplea muticaandM. appendiculata(Coleoptera, Chrysomelidae, Donaciinae) differ in their use ofMyriophyllum spicatumas a host plant

Abstract

The aquatic leaf beetle species Macroplea mutica and M. appendiculata (Coleoptera, Chrysomelidae, Donaciinae) differ in their use of Myriophyllum spicatum as a host plant As a contribution to the continuing discussion of the ecological differentiation and stable coexistence of species, we investigated the extent to which the two sister species, Macroplea mutica and M. appendiculata, use the host plants Myriophyllum spicatum and Potamogeton sp. Specimens from four populations differing in host plant experience were used for behavioural observations. Both species did not feed on Myriophyllum but on Potamogeton. Beetles kept on Myriophyllum or without plant lost weight, while those on Potamogeton maintained or increased their weight. Only M. appendiculata laid eggs on this plant, as well as on Potamogeton, where M. mutica exclusively oviposited. In choice experiments, all larvae preferred the roots of Potamogeton over Myriophyllum for attachment (also the M. mutica larvae that had been collected from Myriophyllum). The data are discussed in the light of the unusual occasional occurrence of M. mutica on Myriophyllum and the speciation in the genus Macroplea.

Sympatric occurrence of three leaf beetle species ofMacropleaSamouelle, 1819 (Coleoptera, Chrysomelidae, Donaciinae) in Finland with a key to species in Northern Europe

“…During summer the adults crawl on water plants or on the bottom at depths of between 20-30 cm to 1.5 m or more. Feeding is scarce in adult Macroplea, according to Kölsch and Kubiak (2011), and limited to Potamogeton species.…”

“…Thus, M. mutica and M. pubipennis were associated with brackish water and M. appendiculata with fresh water. Recently, doubts have been raised about this division because of some records of coexistence of M. mutica and M. appendiculata in both fresh and brackish water from the Baltic region (Kölsch, Krause, Goetz, andPlagmann 2010, Kölsch andKubiak 2011). An extensive survey of Macroplea in fresh waters in the region of Lake Mälaren in Central Sweden was undertaken by Ljungberg et al(2014).…”

“…The occurrence of the species may be influenced by other factors such as plant preference or mechanisms in dispersal, salinity playing a less important role. Kölsch and Kubiak (2011) Most adults collected in the field are found in pairs, male clinging to a female, but the actual copulation is seldom performed and recorded. When the sexes meet they seem to approach each other and remain combined for longer time periods (Kölsch and Kubiak 2011).…”

“…Kölsch and Kubiak (2011) Most adults collected in the field are found in pairs, male clinging to a female, but the actual copulation is seldom performed and recorded. When the sexes meet they seem to approach each other and remain combined for longer time periods (Kölsch and Kubiak 2011). A plausible interpretation of this behaviour is as a method for the male to hinder copulation of the female by other males (e.g., Harari, Landolt, O'Brien, and Brockmann 2003).…”

“…Macroplea species are found on various water plants, but especially in the case of M. pubipennis, it has remained unclear which plants are preferred for development. Earlier information on living habits was mostly at genus level with little exact data on species (e.g., Biström 1996, Biström and Saari 2006, Lou et al 2011, Ljungberg et al 2014Kölsch and Kubiak 2011).…”