Water loss in tree weta (<i>Hemideina</i>): adaptation to the montane environment and a test of the melanisation–desiccation resistance hypothesis

King, Keith; Sinclair, Brent J.

doi:10.1242/jeb.118711

Cited by 25 publications

(22 citation statements)

References 81 publications

(97 reference statements)

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“…Melanin also has benefits associated with ultraviolet (UV) protection (Ortonne, 2002), immunocompetence (Dubovskiy et al, 2013), and desiccation (King & Sinclair, 2015) and its abundance is plastically adjusted in response to increases in these challenges (Wilson et al, 2001;Abram et al, 2015;Välimäki et al, 2015). Variation in these factors may act, like temperature, to enable the persistence of variation in the abundance of melanic morphs across spatial (polytypism) and temporal (polymorphism) scales.…”

Section: The Multifunctionality Of Aposematic Signalsmentioning

confidence: 99%

Diversity in warning coloration: selective paradox or the norm?

et al. 2018

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Aposematic theory has historically predicted that predators should select for warning signals to converge on a single form, as a result of frequency‐dependent learning. However, widespread variation in warning signals is observed across closely related species, populations and, most problematically for evolutionary biologists, among individuals in the same population. Recent research has yielded an increased awareness of this diversity, challenging the paradigm of signal monomorphy in aposematic animals. Here we provide a comprehensive synthesis of these disparate lines of investigation, identifying within them three broad classes of explanation for variation in aposematic warning signals: genetic mechanisms, differences among predators and predator behaviour, and alternative selection pressures upon the signal. The mechanisms producing warning coloration are also important. Detailed studies of the genetic basis of warning signals in some species, most notably Heliconius butterflies, are beginning to shed light on the genetic architecture facilitating or limiting key processes such as the evolution and maintenance of polymorphisms, hybridisation, and speciation. Work on predator behaviour is changing our perception of the predator community as a single homogenous selective agent, emphasising the dynamic nature of predator–prey interactions. Predator variability in a range of factors (e.g. perceptual abilities, tolerance to chemical defences, and individual motivation), suggests that the role of predators is more complicated than previously appreciated. With complex selection regimes at work, polytypisms and polymorphisms may even occur in Müllerian mimicry systems. Meanwhile, phenotypes are often multifunctional, and thus subject to additional biotic and abiotic selection pressures. Some of these selective pressures, primarily sexual selection and thermoregulation, have received considerable attention, while others, such as disease risk and parental effects, offer promising avenues to explore. As well as reviewing the existing evidence from both empirical studies and theoretical modelling, we highlight hypotheses that could benefit from further investigation in aposematic species. Finally by collating known instances of variation in warning signals, we provide a valuable resource for understanding the taxonomic spread of diversity in aposematic signalling and with which to direct future research. A greater appreciation of the extent of variation in aposematic species, and of the selective pressures and constraints which contribute to this once‐paradoxical phenomenon, yields a new perspective for the field of aposematic signalling.

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Section: The Multifunctionality Of Aposematic Signalsmentioning

confidence: 99%

Diversity in warning coloration: selective paradox or the norm?

et al. 2018

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“…Melanin as a barrier to water loss has not been considered for many taxa but it has been widely tested in populations of Drosophila (Parkash, Ramniwas, Rajpurohit, & Sharma, ; Parkash, Singh, & Ramniwas, ). Darker individuals of Drosophila and Hemideina (tree weta; Orthoptera: Anostostomatidae) have performed better than lighter ones under desiccation stress in experimental laboratory conditions (King & Sinclair, ; Parkash et al, , ).…”

Section: Introductionmentioning

confidence: 99%

“…Melanin as a barrier to water loss has not been considered for many taxa but it has been widely tested in populations of Drosophila (Parkash, Ramniwas, Rajpurohit, & Sharma, 2008;Parkash, Singh, & Ramniwas, 2009). Darker individuals of Drosophila and Hemideina (tree weta; Orthoptera: Anostostomatidae) have performed better than lighter ones under desiccation stress in experimental laboratory conditions (King & Sinclair, 2015;Parkash et al, 2008Parkash et al, , 2009. Third, Gloger's rule predicts an increase in melanization (and hence darker colours) in warmer and more humid environments (Rensch, 1929), the opposite of the pattern predicted by the TMH and the MDH.…”

Section: Introductionmentioning

confidence: 99%

Darker ants dominate the canopy: Testing macroecological hypotheses for patterns in colour along a microclimatic gradient

Law

Bishop

Eggleton

et al. 2019

Journal of Animal Ecology

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Gradients in cuticle lightness of ectotherms have been demonstrated across latitudes and elevations. Three key hypotheses have been used to explain these macroecological patterns: the thermal melanism hypothesis (TMH), the melanism‐desiccation hypothesis (MDH) and the photo‐protection hypothesis (PPH). Yet the broad abiotic measures, such as temperature, humidity and UV‐B radiation, typically used to detect these ecogeographical patterns, are a poor indication of the microenvironment experienced by small, cursorial ectotherms like ants. We tested whether these macroecological hypotheses explaining cuticle lightness held at habitat and microclimatic level by using a vertical gradient within a tropical rainforest. We sampled 222 ant species in lowland, tropical rainforest across four vertical strata: subterranean, ground, understory and canopy. We recorded cuticle lightness, abundance and estimated body size for each species and calculated an assemblage‐weighted mean for cuticle lightness and body size for each vertical stratum. Abiotic variables (air temperature, vapour pressure deficit and UV‐B radiation) were recorded for each vertical stratum. We found that cuticle lightness of ant assemblages was vertically stratified: ant assemblages in the canopy and understory were twice as dark as assemblages in ground and subterranean strata. Cuticle lightness was not correlated with body size, and there was no support for the TMH. Rather, we attribute this cline in cuticle lightness to a combination of the MDH and the PPH. Our findings indicate that broad macroecological patterns can be detected at much smaller spatial scales and that microclimatic gradients can shape trait variation, specifically the cuticle lightness of ants. These results suggest that any changes to microclimate that occur due to land‐use change or climate warming could drive selection of ants based on cuticle colour, altering assemblage structure and potentially ecosystem functioning.

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“…Although the melanization increases desiccation resistance of adult insects of different orders (Kalmus, 1941; Parkash et al, 2009; Wittkopp and Beldade, 2009; King and Sinclair, 2015) it is currently unknown if the same process occurs in insect eggs. We investigated here if the intensity of eggshell pigmentation is related to desiccation resistance phenomenon in mosquito vector eggs.…”

Section: Introductionmentioning

confidence: 99%

Darker eggs resist more to desiccation: the case of melanin inAedes,AnophelesandCulexmosquito vectors

Farnesi

Vargas

Valle

et al. 2017

Preprint

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27melanin, mosquito, viability. 28 29 30 31 32 33 34 2 Summary statement: The ability of mosquito eggs of several species to resist differently 35 to dry conditions is investigated. In particular, it unravels why Aedes aegypti eggs survive 36 for several months outside water. Abstract 39 Mosquito vectors lay their eggs in the aquatic milieu. During early embryogenesis water 40 passes freely through the transparent eggshell, composed of exochorion and endochorion. 41 93 Curiously, the level of egg resistance to desiccation (ERD) varies among mosquito species 94 at the end of embryogenesis: while Ae. aegypti eggs can survive for at least 72 hours in a 95 dry environment (high ERD), those of An. aquasalis and Cx. quinquefasciatus in the same 96 condition can survive, respectively, for 24 hours (medium ERD) and 5 hours (low ERD) 97 (Figure 1C) (Vargas et al., 2014). Physical and biochemical features of these eggs were 98 investigated in order to identify traits related with these differences. Chitin content is 99 directly related to ERD levels while both egg volume increase during embryogenesis and 100 eggshell superficial density are inversely related to. Moreover, other yet unidentified traits 101 might also be relevant (Farnesi et al., 2015).102 4Although the melanization increases desiccation resistance of adult insects of different 103 orders (Kalmus, 1941; Parkash et al., 2009; Wittkopp and Beldade, 2009; King and 104 Sinclair, 2015) it is currently unknown if the same process occurs in insect eggs. We 105 investigated here if the intensity of eggshell pigmentation is related to desiccation 106 resistance phenomenon in mosquito vector eggs.

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Water loss in tree weta (Hemideina): adaptation to the montane environment and a test of the melanisation–desiccation resistance hypothesis

Cited by 25 publications

References 81 publications

Diversity in warning coloration: selective paradox or the norm?

Diversity in warning coloration: selective paradox or the norm?

Darker ants dominate the canopy: Testing macroecological hypotheses for patterns in colour along a microclimatic gradient

Darker eggs resist more to desiccation: the case of melanin inAedes,AnophelesandCulexmosquito vectors

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