Tropical Origin, Global Diversification and Dispersal in the Pond Damselflies (Coenagrionoidea) Revealed by a New Molecular Phylogeny

Abstract

Aim: The processes responsible for the formation of Earth's most conspicuous diversity pattern, the latitudinal diversity gradient (LDG), remain unexplored for many clades in the Tree of Life. Here, we present a densely-sampled and dated molecular phylogeny for the most speciose clade of damselflies worldwide (Odonata: Coenagrionoidea), and investigate the role of time, macroevolutionary processes and dispersal dynamics in shaping the LDG in this ancient insect superfamily. Location: global. Time period: 240-0 mya. Major taxa studied: pond damselflies (Coenagrionidae) and featherlegs (Platycnemididae). Methods: We used a process-based biogeographic model to jointly infer ancestral ranges and speciation times and to characterise dispersal dynamics between latitudinal regions. We then used this phylogenetic inference to investigate temporal and latitudinal variation in diversification rates. Results: Our results uncover a tropical origin of pond damselflies and featherlegs ~ 105 mya, with their common ancestor arising in either Northern South America or Western Africa. While diversification rates have declined since the origin of this clade, the tropics have acted as a net source of lineages dispersing into temperate areas, where both speciation and extinction rates have been relatively higher. Main conclusions: This study underscores the importance of biogeographic origin and time to diversify as important drivers of the LDG in pond damselflies. Diversification dynamics may have instead resulted in the formation of ephemeral species in temperate regions. Dispersal has played a role reducing the steepness of the LDG, rather than amplifying it, which would have been expected under strong tropical niche conservatism. With ongoing climate change and increasing northward range expansions of many damselfly taxa, the LDG may continue to shallow. Our results support recent calls to unify biogeographic and macroevolutionary approaches to increase our understanding of how latitudinal diversity gradients are formed and why they vary across time and among taxa.

Phylogeny and classification of Nesobasis Selys, 1891 and Vanuatubasis Ober & Staniczek, 2009 (Odonata: Coenagrionidae)

“…Coenagrionidae, a family of damselflies consisting of over 1300 species (Dijkstra et al 2014;Schorr & Paulson 2018;Paulson 2019;Paulson et al 2022) has been studied for over 150 years (O'Grady & May 2003); a solid taxonomic understanding of this family is lacking, but a recent study brings some clarity (Willink et al 2022). Subjectivity within character states, lack of apparent diagnostic features, and classification schemes have exacerbated the problem, especially when addressing the taxonomy of island damselflies, as these systems are often the most underworked and incomplete.…”