O valor do recurso influencia a evolução do pré-pólex em forma de espinho? Um teste em rãs-gladiadoras (Anura: Hylidae: Cophomantini)
Data
2022-08-30
Autores
Candaten, Aline 
Orientadores
Palaoro, Alexandre Varaschin
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Confrontos são comuns na natureza e ocorrem pela posse de um recurso indivisível. Indivíduos que vencem os confrontos garantem acesso aos recursos que aumentam sua aptidão. Nas espécies em que confrontos são frequentes, é comum os indivíduos possuírem estruturas morfológicas que ajudam na vitória. Apesar da importância para a vitória, injúrias são raras em confrontos animais. Mas, alguns armamentos como o pré-pólex das rãs-gladiadoras parecem mais propensos a causá-las do que outros armamentos. Uma hipótese proeminente na literatura é de que armamentos podem evoluir quando o recurso disputado é valioso para o indivíduo. Portanto, é esperado que armamentos potencialmente injuriosos, como o pré-pólex em forma de espinho, evoluiriam quando o recurso sendo disputado fosse extremamente valioso. Em anuros, os machos disputam a dominância de locais de oviposição. A exposição destes ambientes aumenta a propensão do indivíduo defender aquela área, pois quanto mais exposto o recurso maior é a interação entre rivais que podem roubar a paternidade. Além disso, quando os locais de oviposição são construídos pelos machos, o investimento de tempo e energia gastos na construção aumentam a territorialidade pela defesa do ninho. Nesta dissertação, testei se o valor do recurso estava associado à forma de pré-pólex mais injuriosa. Mais especificamente, testei se a exposição e a construção do recurso estavam associadas ao pré-pólex em forma de espinho na tribo Cophomantini. Antes de testar minha hipótese, realizei uma revisão sistemática do pré-pólex e do seu potencial injurioso. Feito isso, realizei a reconstrução do estado ancestral do pré-pólex e da elaboração do local de oviposição. Segundo, avaliei a correlação entre os caracteres discretos usando o modelo de Threshold. Em seguida, usei uma regressão logística filogenética para testar a relação destas características. Os resultados mostram que: (i) O prépólex em forma de espinho é mais injurioso do que o pré-pólex de forma laminar; (ii) O estado ancestral mais provável é o pré-pólex laminar associado ao comportamento de não construir ninhos; (iii) O pré-pólex é evolutivamente estável dentro da filogenia apresentando apenas 1-2 reversões para a condição ancestral; (iv) A variação na morfologia do pré-pólex não foi explicada pelo efeito do valor do recurso e não há relação entre o surgimento do armamento injurioso com o comportamento de briga pelo recurso reprodutivo. Essas evidências somadas sugerem que, por mais que os indivíduos usem este armamento durante os confrontos, ele não evoluiu por causa dos confrontos. Uma possível explicação para os resultados encontrados neste trabalho é que o espinho é uma estrutura barata para se manter e que as condições atuais não exercem pressão seletiva para a reversão da estrutura. Os armamentos de outras linhagens parecem seguir rotas evolutivas similares, sendo originados para uma função e depois exaptados para confrontos. Portanto, apesar da injúria ser incomum em armamentos, é possível que isso tenha ocorrido porque a estrutura exaptada causava injúrias - algo que não ocorre normalmente em outros armamentos que tipicamente são versões exageradas de apêndices.
Contests are common in nature and occur for the possession of an indivisible resource. Individuals who win contests ensure access to resources that increase their fitness. In species in which contests are frequent, it is common for individuals to possess morphological structures that help winning. Despite the importance of victory in taxa that engage in contests, injuries are rare across animals. Some weapons like the prepollex of gladiator frogs seem more likely to cause damage than other weapons. A prominent hypothesis in the literature is that weapons can evolve when the disputed resource is valuable to the individual. Therefore, it is expected that potentially injurious weapons, such as prepollex spine, would evolve when the resource being disputed is extremely valuable. In frogs, males compete for dominance of oviposition sites. How exposed these environments are increases the individual's propensity to defend that area, because the more exposed the resource, the greater the interaction between rivals who can steal paternity. Furthermore, when oviposition sites are built by males, the investment of time and energy spent in construction increases territoriality by defending the nest. In this dissertation, I tested if resource value was associated with the most injurious prepollex form. More specifically, I tested if exposure and building oviposition sites were associated with spine-shaped prepollex in the Cophomantini tribe. Before testing my hypothesis, I performed a systematic review of prepollex and its injurious potential. After that, I reconstructed the ancestral state of the prepollex and building the oviposition site. Second, I evaluated the correlation between the discrete characters using the Threshold model. Next, I used a phylogenetic logistic regression to test the relationship of these traits. My results show that: (i) The spine-shaped prepollex is more injurious than the laminar-shaped prepollex; (ii) The ancestral state with highest probability is the laminar prepollex associated with the behavior of not building nests; (iii) The prepollex is evolutionarily stable in the phylogeny showing only 1-2 reversions to the ancestral condition; (iv) The variation in prepollex morphology was not explained by the effect of resource value and there is no relationship between the emergence of injurious weaponry and fighting behavior for the reproductive resource. These evidences suggest that even though this weapon is used during contests, it has not evolved because of contests. A possible explanation is that the spine is metabolically cheap to maintain and that current conditions might not impose selection on the structure to change. Weapons from other animal lineages (e.g., horns, claws) appear to follow similar evolutionary routes, being originated for a function and then exapted for contests. Therefore, although injury is uncommon in weapons, it is possible that this event occurred in Cophomantini because the exapted structure caused injuries - something that does not normally occur in other weapons that are typically exaggerated versions of appendages.
Contests are common in nature and occur for the possession of an indivisible resource. Individuals who win contests ensure access to resources that increase their fitness. In species in which contests are frequent, it is common for individuals to possess morphological structures that help winning. Despite the importance of victory in taxa that engage in contests, injuries are rare across animals. Some weapons like the prepollex of gladiator frogs seem more likely to cause damage than other weapons. A prominent hypothesis in the literature is that weapons can evolve when the disputed resource is valuable to the individual. Therefore, it is expected that potentially injurious weapons, such as prepollex spine, would evolve when the resource being disputed is extremely valuable. In frogs, males compete for dominance of oviposition sites. How exposed these environments are increases the individual's propensity to defend that area, because the more exposed the resource, the greater the interaction between rivals who can steal paternity. Furthermore, when oviposition sites are built by males, the investment of time and energy spent in construction increases territoriality by defending the nest. In this dissertation, I tested if resource value was associated with the most injurious prepollex form. More specifically, I tested if exposure and building oviposition sites were associated with spine-shaped prepollex in the Cophomantini tribe. Before testing my hypothesis, I performed a systematic review of prepollex and its injurious potential. After that, I reconstructed the ancestral state of the prepollex and building the oviposition site. Second, I evaluated the correlation between the discrete characters using the Threshold model. Next, I used a phylogenetic logistic regression to test the relationship of these traits. My results show that: (i) The spine-shaped prepollex is more injurious than the laminar-shaped prepollex; (ii) The ancestral state with highest probability is the laminar prepollex associated with the behavior of not building nests; (iii) The prepollex is evolutionarily stable in the phylogeny showing only 1-2 reversions to the ancestral condition; (iv) The variation in prepollex morphology was not explained by the effect of resource value and there is no relationship between the emergence of injurious weaponry and fighting behavior for the reproductive resource. These evidences suggest that even though this weapon is used during contests, it has not evolved because of contests. A possible explanation is that the spine is metabolically cheap to maintain and that current conditions might not impose selection on the structure to change. Weapons from other animal lineages (e.g., horns, claws) appear to follow similar evolutionary routes, being originated for a function and then exapted for contests. Therefore, although injury is uncommon in weapons, it is possible that this event occurred in Cophomantini because the exapted structure caused injuries - something that does not normally occur in other weapons that are typically exaggerated versions of appendages.
Descrição
Citação
CANDATEN, Aline. O valor do recurso influencia a evolução do pré-pólex em forma de espinho? Um teste em rãs-gladiadoras (Anura: Hylidae: Cophomantini). 2022. 41 f. Dissertação (Mestrado em Ecologia e Evolução) - Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo, Diadema, 2022.