Condition-dependent trade-offs between sexual traits, body condition and immunity: the effect of novel habitats

Abstract

BackgroundThe optimal allocation of resources to sexual signals and other life history traits is usually dependent on an individual’s condition, while variation in the expression of sexual traits across environments depends on the combined effects of local adaptation, mean condition, and phenotypic responses to environment-specific cues that affect resource allocation. A clear contrast can often be drawn between natural habitats and novel habitats, such as forest plantations and urban areas. In some species, males seem to change their sexual signals in these novel environments, but why this occurs and how it affects signal reliability is still poorly understood.ResultsThe relative size of sexual traits and level of immune responses were significantly lower for male palmate newts Lissotriton helveticus caught in pine and eucalyptus plantations compared to those caught in native forests, but there was no habitat-dependent difference in body condition (n = 18 sites, 382 males). The reliability with which sexual traits signalled body condition and immune responses was the same in all three habitats. Finally, we conducted a mesocosm experiment in which males were maintained in pine, eucalypt or oak infused water for 21 days. Males in plantation-like water (pine or eucalypt) showed significantly lower immune responses but no change in body condition. This matches the pattern seen for field-caught males. Unlike field-caught males, however, there was no relationship between water type and relative sexual trait size.ConclusionsPine and eucalyptus plantations are likely to be detrimental to male palmate newt because they are associated with reduced immune function and smaller sexual traits. This could be because ecological aspects of these novel habitats, such as high water turbidity or changes in male-male competition, drive selection for reduced investment into sexual traits. However, it is more probable that there are differences in the ease of acquisition, hence optimal allocation, of resources among habitats. Our mesocosm experiment also provides some evidence that water toxicity is a causal factor. Our findings offer insights into how plantations affect amphibian life histories, and how novel habitats might generate long-term selection for new resource allocation strategies in native species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0706-0) contains supplementary material, which is available to authorized users.

Eucalypt leaf litter impairs growth and development of amphibian larvae, inhibits their antipredator responses and alters their physiology

“…Surprisingly, despite the large extent of eucalypt reforestations worldwide, the effects of eucalypt plantations on aquatic vertebrates (and particularly on amphibians) have received very little attention (but see Iglesias-Carrasco et al , 2016 and Iglesias-Carrasco et al , 2017a ). Although it has recently been shown that eucalypt leaf litter can impair mate and predator recognition in adult newts ( Iglesias-Carrasco et al , 2017b ), the extent to which it also affects growth, development or physiology of amphibian larvae is virtually unknown.…”

Effect of an immune challenge on the anti-predator response of the green Iberian frog (Pelophylax perezi): the influence of urban habitats

“…While some studies find both larger (Liker et al, 2008) and smaller (Murphy et al, 2016) body sizes in urban populations in different animal taxa, others do not find any effect of urbanization on this trait (Iglesias-Carrasco et al, 2017). Similarly, previous research has found that colonizers of anthropogenic habitats show either enhanced (French et al, 2007b;Audet, Ducatez & Lefebvre, 2016) or diminished immunocompetence (Lewis et al, 2013;Iglesias-Carrasco et al, 2016a) compared to their counterparts in natural habitats. These contrasting findings highlight the difficulty of making predictions about the potential effects of urbanization on morphological and physiological traits.…”

Leaf extracts from an exotic tree affect responses to chemical cues in the palmate newt, Lissotriton helveticus

“…It is now clear that these substances can be toxic and adversely affect several ecological and physiological aspects of fish (Steinberg et al, 2006), aquatic invertebrates (Larrañaga, Basaguren, Elosegi, & Pozo, 2009) and amphibians (Iglesias-Carrasco, Head, Jennions, & Cabido, 2016). Even species that naturally occur in waterways in eucalypt forests, such as some fish, have reduced growth and survival when they are exposed to the toxic leachates found in these habitats (Morrongiello, Bond, Crook, & Wong, 2013).…”