Jesús Martínez-Padilla - Behavioural and evolutionary ecologist

Sexual selection

Sexual selection

Main collaborators: Prof. J. Potti; Dr. F. Mougeot; Dr. Juan A. Fargallo; Dr. Lorenzo Pérez-Rodríguez and Dr-to-be Carlos Camacho

I am interested in the physiological mechanisms that produce variation of sexual traits, behavioural functions and evolutionary meaning of sexual behaviour.

 

The expression of secondary sexual traits entails a cost on their bearers, including physiological or behavioural costs. For example, showing-off may cause a cost of predation because individuals become more conspicuous, risk of parasitism because individuals increase their exposure/susceptibility to parasites or may alter physiological trade-offs diverting more resources to ornamentation than for other energetically functions like immune defence. This cost is crucial in sexual selection, because it ensures the evolution of sexual traits where only high-quality individuals are able to stand the cost imposed by the extravagant expression of sexual traits. I have used red grouse and common kestrels as study species, manipulating their natural levels of hormones and parasites.

 

However, there are four particular issues that I am quite interested in:

 

1. The cost of producing a sexual signal might be environment-dependent. If all individuals in a population live in a favourable environment (no parasites, no predators, food ad-libitum, etc), the cost of producing a sexual signal is not expected to be as different between high- and low-quality individuals as theory might predict. We explored these issues in red grouse [24, 30, 31, 33, 34, 35, 43, 44] and currently David López is carrying out his PhD on this matter using female kestrels as study species.

 

2. Do females face a cost when they express a sexual signal? Most of the theory on the evolution and behavioural meaning of sexual selection has been incredibly biased on males, but very little is known in females. I am quite interested in exploring the behavioural and evolutionary meaning of sexual traits in females, and the factors that may mediate their expression [20, 28, 35].

3. Finally, it is obvious that we see coloured birds and that the variation of such colouration is due to well-known factors (hormones, parasites, social context, etc...), but what is its evolutionary meaning? The three pillars of natural selection lays on variation of the trait, their association with fitness traits and their heritability. In other words, we need to know how these signals are associated with fitness traits in a population and how they are transmitted from one generation to the next. Only studying these last two bits, we can start understanding how evolution works. Linking this idea with the previous point, I am very interested in exploring how environmental variation is the engine that makes evolution work, that is understanding how environmental variation influences additive genetic variation and selection on sexual traits under changing environmental conditions. To do so, I use long-term monitored populations of Common kestrels and Pied flycatchers as study species and quantitative genetic tools to address these complex issues. You can find an example here and keep an eye on updates because there are more coming soon...

4. Sometimes, males and females do differ in their interests what may result in a sexual conflict to maximise their  fitness of one sex at the expenses of the other. This is broadly known as sexual conflict. Currently, in collaboration (supervision mostly) with Dr. F. García-González, I am exploring the evolutionary potential of certain signals involved in sexual conflict in Cowpea seed beetles (Callosobruchus maculatus).

 

All photographs shown here are of my own unless stated otherwise - I have also designed the entire web site, so this is © Jesús Martínez-Padilla