First Insights into the Phylogeny of the Pygmy Backswimmers (Pleidae: Hemiptera: Heteroptera)



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Members of the family Pleidae are known as pygmy backswimmers and are part of the aquatic hemipteran clade Nepomorpha with two other families: Notonectidae and Helotrephidae. Current knowledge of the taxonomy and evolutionary history of the family Pleidae is complicated and understudied. The first record of a member of the family Pleidae dates to 1817, and the first species, Plea leachi was placed in the family Notonectidae in 1817 (Leach 1817). In 1851, Fieber erected Pleae as a subfamily in Notonectidae, even though Pleids were more like Helotrephidae (Fieber 1851; Cook 2011). The family Pleidae was erected as its own family, outside of Notonectidae, in 1928 with the addition of new genera Neoplea and Paraplea (Eskai & China 1928). These subgenera were based on a formula of tarsal segment numbers, designating each genus with their own specific tarsal formula: Plea has a tarsal formula of 3, 3, 3, Neoplea has a tarsal formula of 3, 2, 3, and Paraplea has a tarsal formula of 3, 2, 2 (Eskai & China 1928). As research continued, a fourth genus, Heteroplea, was erected in 2011 (Cook), which shared the same tarsal formula as Plea. The erection of this genus posed the question of whether the tarsal formula is a good defining character for genera. Researchers noted that other characters, such as the presence of a claval suture and color patterns, were also variable and pose concerns identical to that of the tarsal formula, however these issues are still unresolved. This research attempts to resolve the issues at hand as well as test the monophyly with the first insights to a morphological phylogeny of the family Pleidae. The results of this research yielded the first insights to a phylogeny of the family Pleidae with 100 most parsimonious trees. A consensus tree with Jackknife and Bremer support values is presented, showing low support for the most parsimonious trees. No taxonomic changes were made, all results presented were based on the “best” most parsimonious tree.



Biology, Entomology