中華珈蟌替代性繁殖策略與型值特徵的相關性

Abstract

替代性繁殖策略( alternative reproductive tactics, ARTs )是指雄性物種透過不同的形態及行為等，來增加交配成功的機會。在蜻蛉中，成熟雄性以環境資源或自體能量為依據使用不同的繁殖策略 (領域型、無領域型／徘徊型／潛行型，或是於兩者間搖擺)。在近期分化的蜻蛉，透過性擇所形成之不同繁殖策略的演化，可能加速其種化的過程。然而，我們對於在高度相近但表型分化的蜻蛉物種之間，ARTs的相對影響所知甚少。本研究調查台灣豆娘兩鄰域分布的亞種：中華珈蟌 (Psolodesmus mandarinus)指名亞種 (P. m. mandarinus) 及南台亞種 (P. m. dorothea) ，探討其ARTs的起因及結果。調查結果指出，兩亞種雄性均利用相同的三種繁殖策略，包含領域型 (territorial)、無領域型 (non-territorial) ，及搖擺型 (switching)。在福山植物園的指名亞種族群中，增加體重和減少後翅面積，與增加領域性相關。相較於無領域型雄性，領域型及搖擺型雄性有較高的交配機會 (即最少交配過一次)。然而，僅搖擺型雄性而不是領域型雄性，相對於無領域型個體有較高的交配成功。相較之下，蓮華池中南台亞種族群，則沒有任何身體形質和領域性相關。僅搖擺型雄蟲，而非領域性雄蟲，相較於無領域型個體有較高交配機會。南台亞種雄性的三種繁殖策略對其交配成功沒有顯著影響。在兩中華珈蟌亞種，搖擺型雄蟲而非領域型雄蟲有較高適存度 (fitness)。結果顯示在形態特徵與適存度和ARTs的相關性上，可能是由於棲地差異或觀察者效應導致。Males of the many animal species use alternative reproductive tactics (ARTs) to obtain mating opportunity and reproductive success. In odonate species, adult males employ various genetically or conditionally based mating tactics (territoriality, non-territoriality/wandering/sneaking, or switching between the two). The evolution of different ARTs via sexual selection in recently diverged odonate species may have facilitated their speciation process. However, the relative effects of the ARTs between closely related but phenotypically divergent odonate species is poorly known. This study investigated the causes and consequences of the ARTs in two parapatrically distributed subspecies of Taiwanese Psolodesmus mandarinus damselflies, P. m. mandarinus and P. m. dorothea. The observations indicate that the males of both subspecies employ the same three mating tactics, including territorial, switching, and non-territorial. In P. m. mandarinus population of Fusan, an increase in body mass and decrease in hindwing area is associated with an increase in territoriality. Compared to non-territorial males, territorial and switching P. m. mandarnus males have higher mating opportunity (i.e. to engage in at least one mating). However, only switching but not territorial P. m. mandarnus males have higher mating success than non-territorial males. In contrast, none of the body size indicators are associated with territoriality in P. m. dorothea population of Lianhuachi. Only the switching but not territorial P. m. dorothea males had higher mating opportunity than non-territorial males. The mating tactics of P. m. dorothea males had no significant effect on their mating success. In both P. mandarinus subspecies, the switching males instead of territorial males, appear to have the highest fitness. These results suggest that the ARTs of the two P. mandarinus subspecies were different in their associations of morphological traits and fitness consequences, which may be due to habitat differences or observer effects.