Continental variation in wing pigmentation in Calopteryx damselflies is related to the presence of heterospecifics

Abstract

Continental variation in wing pigmentation in Calopteryx damselflies is related to the presence of heterospecificsWing pigmentation in Calopteryx damselflies, caused by the deposition of melanin, is energetically expensive to produce and enhances predation risk. However, patterns of melanisation are used in species identification, greater pigmentation is an accurate signal of male immune function in at least some species, and there may be a role for pigment in thermoregulation. This study tested two potential hypotheses to explain the presence of, and variation in, this pigmentation based on these three potential benefits using 907 male specimens of Calopteryx maculata collected from 49 sites (34 discrete populations) across the geographical range of the species in North America: (i) pigmentation varies with the presence of the closely related species, Calopteryx aequabilis, and (ii) pigment increases at higher latitudes as would be expected if it enhances thermoregulatory capacity. No gradual latitudinal pattern was observed, as might be expected if pigmentation was involved in thermoregulation. However, strong variation was observed between populations that were sympatric or allopatric with C. aequabilis. This variation was characterised by dark wings through allopatry in the south of the range and then a step change to much lighter wings at the southern border of sympatry. Pigmentation then increased further north into the sympatric zone, finally returning to allopatry levels at the northern range margin. These patterns are qualitatively similar to variation in pigmentation in C. aequabilis, meaning that the data are consistent with what would be expected from convergent character displacement. Overall, the results corroborate recent research that has suggested sexual selection as a primary driver behind the evolution of wing pigmentation in this group. PeerJ PrePrints

Body temperature regulation is associated with climatic and geographical variables but not wing pigmentation in two rubyspot damselflies (Odonata: Calopterygidae)

“…The findings of previous studies lend some support to the concept that, along with sexual selection, wing pigmentation spots in calopterygids can be naturally selected via an increasing body temperature (Outomuro & Ocharan, ; Svensson & Waller, ; but see also Hassall, ). By contrast, the results of the present study for the two Hetaerina species indicate that spot colour aspect does not explain temperature changes and that spot size does not lead to increases in body temperature, the temperature needed to fly, or how long it takes to achieve flight, and is not related to seasonality and altitude.…”

“…In these animals, wing pigmentation spots are used by males to convey information concerning: territory possession (González‐Santoyo et al , ) and/or fighting ability over territory ownership (Grether, ; Contreras‐Garduño et al , ) to other males; the ability to resist pathogens (Siva‐Jothy, ; Rantala et al , ); and mate guarding ability (Siva‐Jothy, ) to females. Despite support for a sexual selection advantage, there are limited studies testing whether calopterygid pigmentation is also explained by two alternative hypotheses: species recognition (Waage, ; Svensson et al , ; Tynkkynen et al , ; Hassall, ) and temperature gain (Outomuro & Ocharan, ; Svensson & Waller, ).…”

When morphological identification meets genetic data: the case ofLucanus cervusandL. tetraodon(Coleoptera, Lucanidae)

“…‘Convergent character displacement’ (Grant ) has been hypothesized when the character states of sympatric species may be selected to converge. This phenomenon, the opposite of the more common and well‐documented ‘divergent character displacement’ (Brown and Wilson ; Grant ; Waage ; Butlin ; Howard ; Hostert ; Kawano ), has been described in some vertebrates and invertebrates (Vadas ; Scott and Foster ; Leary ; Hassall ). A reproductive advantage of hypothelic males with respect to hyperthelic ones has been suggested for L. cervus (Harvey and Gange ), and a morphological convergence of L. cervus and L. tetraodon in areas of syntopic occurrence may reflect a similar advantage.…”

“…The latter phenomenon has been defined as ‘convergent character displacement’ (Grant ). The character states of sympatric species may be selected to converge, even though few cases have been described thus far in vertebrates and invertebrates (Vadas ; Scott and Foster ; Leary ; Hassall ) with respect to the more common ‘divergent character displacement’ (Brown and Wilson ; Grant ; Butlin ; Howard ; Hostert ; Kawano ).…”

Peer Review #2 of "Strong geographical variation in wing aspect ratio of a damselfly, Calopteryx maculata (Odonata: Zygoptera) (v0.1)"

“…The results presented here demonstrate clear geographical variation in flight morphology in a damselfly across almost its entire range. While the other studies investigating geographical variation in odonate morphology have focused on north-south transects (Johansson 2003), there are clearly important patterns occurring along the east-west axis of the range highlighting the need to consider range-wide surveys to understand macroecological and macroevolutionary patterns (Hassall 2013(Hassall , 2014. From the survey of studies that have included aspect ratio, it is clear that laboratory studies are needed to clarify the relationship between form and function in odonate wing shape.…”