Sympatric speciation by allochrony in a seabird

Abstract

The importance of sympatric speciation (the evolution of reproductive isolation between codistributed populations) in generating biodiversity is highly controversial. Whereas potential examples of sympatric speciation exist for plants, insects, and fishes, most theoretical models suggest that it requires conditions that are probably not common in nature, and only two possible cases have been described for tetrapods. One mechanism by which it could occur is through allochronic isolation-separation of populations by breeding time. Oceanodroma castro (the Madeiran or bandrumped storm-petrel) is a small seabird that nests on tropical and subtropical islands throughout the Atlantic and Pacific Oceans. In at least five archipelagos, different individuals breed on the same islands in different seasons. We compared variation in five microsatellite loci and the mitochondrial control region among 562 O. castro from throughout the species' range. We found that sympatric seasonal populations differ genetically within all five archipelagos and have ceased to exchange genes in two. Population and gene trees all indicate that seasonal populations within four of the archipelagos are more closely related to each other than to populations from the same season from other archipelagos; divergence of the fifth sympatric pair is too ancient for reliable inference. Thus, seasonal populations appear to have arisen sympatrically at least four times. This is the first evidence for sympatric speciation by allochrony in a tetrapod, and adds to growing indications that population differentiation and speciation can occur without geographic barriers to gene flow.Oceanodroma castro ͉ phylogeography ͉ genetic isolation ͉ seasonal populations ͉ storm-petrel

Asynchrony of Seasons: Genetic Differentiation Associated with Geographic Variation in Climatic Seasonality and Reproductive Phenology

“…Therefore, because organisms seek to reproduce during peaks of high resource availability (Wingfield et al 1992;Durant et al 2007;Dunn et al 2011), even if precipitation is not the main cue used by birds to activate their phenology, other cues used to predict environmental fluctuations in food abundance are likely coupled with precipitation regimes. We acknowledge, however, that although substantial evidence supports the match between reproductive phenology and food abundance (Dittami and Gwinner 1985;Gwinner 2003), food may not be the ultimate force triggering reproduction; in some cases, predation rates or intraspecific competition might play a more prominent role (Wingfield et al 1992;Ahumada 2001;Friesen et al 2007).…”

“…Evidence for allochronic speciation exists for organisms such as insects, fish, and plants (Alexander and Bigelow 1960;Simon et al 2000;Ritchie 2001;Devaux and Lande 2008;Yamamoto and Sota 2009). For birds and other tetrapods, we are aware of only one example of allochronic speciation, which involves sympatric seabirds (Friesen et al 2007). Importantly, the ASH does not propose that asynchrony in breeding phenology is the first step toward sympatric allochronic speciation; instead, more generally, such asynchrony is a factor preventing populations connected by dispersal from effectively exchanging genes if they occur under different precipitation regimes, even if they occur in allopatry.…”

The clock gene cryptochrome of Bactrocera cucurbitae (Diptera: Tephritidae) in strains with different mating times

“…In the wild, temporal reproductive isolation results from differences in mating season in birds (Friesen et al, 2007), mating period in insects (Bush, 1969;Hendry et al, 2000), timing of gamete release in corals (Levitan et al, 2004), timing of migration and breeding in fishes , and time of mating in flies .…”

Hybridization masks speciation in the evolutionary history of the Galápagos marine iguana

“…Therefore, these systems can be seen as evolutionary laboratories, and provide a more simplified framework to study evolutionary processes than mainland settings. Prime examples of island-based evolutionary research include well-known adaptive radiations [2][3][4]], Mayr's classical work on allopatric species formation [5] and compelling accounts of within-island speciation [6][7][8]. However, island systems do not only provide useful settings to study diversification processes leading to speciation-they also reveal insights into the processes which counteract speciation, such as hybridization.…”