Banca de DEFESA: Pedro Nascimento Rocha

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Pedro Nascimento Rocha
DATE: 15/03/2023
TIME: 10:00
LOCAL: Auditório 2 do Instituto de Ciências Biológicas
TITLE:

Sexual Size Dimorphism Evolution in Thomisidae (Araneae) and Trichonephila clavipes (Araneae: Araneidae)

KEY WORDS:

Sexual size dimorphism; spiders; foraging strategies; scrambled competition

PAGES: 115
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

Size sexual dimorphism (SSD) is a phenomenon that occurs in almost all animal groups. Female-biased dimorphism, that is, females larger than males, is the most common, occurring in most species. Spiders, in particular, have the highest femalebiased SSD among terrestrial animals. The gigantism of females in this group is commonly associated with fecundity selection, a hypothesis that predicts that larger females lay more eggs, and consequently have greater fitness. However, for the evolution of the SSD, in addition to the change in the body size of one sex, it is necessary that the other does not accompany it. The differential equilibrium model proposes that different evolutionary pressures act on the body size of the sexes, when these pressures are antagonistic, the SSD evolves. We investigated the evolution of sexual dimorphism in spiders, using the family Thomisidae and the species Trichonephila clavipes (Araneidae) to assess how these evolutionary pressures act on the size of each sex. In the family Thomisidae, we aimed to identify which factors are responsible for the increase in female body size. Large bodies need more energy to sustain themselves, the Thomisidae family has a wide range of foraging strategies, some, such as foraging on flowers and aggressive mimicry, can provide higher energy intake and allow for an increased body size. To carry out this work, we extracted tomisids measurements of the size from the literature, and classified them into foraging strategies. Our results indicate that species that forage on flowers or adopt aggressive mimicry have significantly larger females and significantly smaller males than other species. These results suggest that foraging strategies play a central role in the evolution of SSD. In T. clavipes we aim to evaluate which pressures prevent males from increasing in size with females. Two complementary hypotheses have been proposed as limiting male size, protandry and the gravity hypothesis. Protandry as a way to limit male size suggests that males that develop faster have reproductive advantages in a context of scrambled competition, males with shorter development can reach females with little or no competition. The gravity hypothesis proposes that there is a positive relationship between size and climbing speed, up to a limit where increasing size does not favor climbing speed. We hypothesize that there is a trade-off between protandry and climbing speed in T. clavipes. To test this hypothesis, we accompanied T. clavipes from five localities and evaluated the size of males during the reproductive period. To evaluate the effect of size on climbing speed, we performed climbing experiments with males and females. Our results indicate that protandrous males are larger than late males, and also, that there is a positive relationship between climbing speed and size for males, but not for females. These results indicate that larger males have higher fitness, but that the size of males might be limited by the impacts of gravity on their mobility, as females, much larger than males, do not gain climbing advantages due to their increased size.

BANKING MEMBERS:
Externa à Instituição - CAMILA VIEIRA CURTI - USP
Presidente - 1460864 - FELIPE MALHEIROS GAWRYSZEWSKI
Interna - 2476936 - MARINA REGINA FRIZZAS
Interno - 020.440.331-60 - PEDRO DINIZ ALVES - UnB