Data from: Age estimates for an adaptive lake fish radiation, its mitochondrial introgression, and an unexpected sister group: Sailfin silversides of the Malili Lakes system in Sulawesi

Background: The Malili Lakes system in central Sulawesi (Indonesia) is a hotspot of freshwater biodiversity in the Wallacea, characterized by endemic species flocks like the sailfin silversides (Teleostei: Atherinomorpha: Telmatherinidae) radiation. Phylogenetic reconstructions of these freshwater fishes have previously revealed two Lake Matano Telmatherina lineages (sharpfins and roundfins) forming an ancient monophyletic group, which is however masked by introgressive hybridization of sharpfins with riverine populations. The present study uses mitochondrial data, newly included taxa, and different external calibration points, to estimate the age of speciation and hybridization processes, and to test for phylogeographic relationships between Kalyptatherina from ancient islands off New Guinea, Marosatherina from SW Sulawesi, and the Malili Lakes flock. Results: Contrary to previous expectations, Kalyptatherina is the closest relative to the Malili Lakes Telmatherinidae, and Marosatherina is the sister to this clade. Palaeogeographic reconstructions of Sulawesi suggest that the closer relationship of the Malili Lakes radiation to Kalypatherina might be explained by a 'terrane-rafting' scenario, while proto-Marosatherina might have colonized Sulawesi by marine dispersal. The most plausible analysis conducted here implies an age of c. 1.9 My for the onset of divergence between the two major clades endemic to Lake Matano. Diversification within both lineages is apparently considerably more recent (c. 1.0 My); stream haplotypes present in the sharpfins are of even more recent origin (c. 0.4 My). Conclusions: Sulawesi's Telmatherinidae have most likely originated in the Sahul Shelf area, have possibly reached the island by both, marine dispersal and island/terrane-rafting, and have colonized the Malili Lakes system from rivers. Estimates for the split between the epibenthic sharpfins and the predominantly pelagic to benthopelagic roundfins in Lake Matano widely coincide with geological age estimates of this rift lake. Diversification within both clades clearly predates hybridization events with stream populations. For Lake Matano, these results support a scenario of initial benthic-pelagic divergence after colonization of the lake by riverine populations, followed by rapid radiation within both clades within the last 1 My. Secondary hybridization of stream populations with the sharpfins occurred more recently, and has thus most likely not contributed to the initial divergence of this benthic species flock.Background: 马拉利湖系（Malili Lakes system）位于印度尼西亚苏拉威西中部，是华莱士区（Wallacea）淡水生物多样性热点区域，以旗银汉鱼科（Telmatherinidae，Teleostei: Atherinomorpha）的辐射演化类群等特有类群集群为典型特征。此前针对此类淡水鱼类的系统发育重建（phylogenetic reconstructions）研究显示，马塔诺湖的两种Telmatherina支系（尖鳍型与圆鳍型）构成一个古老的单系群，但尖鳍型与河流种群的渐渗杂交（introgressive hybridization）掩盖了这一单系关系。本研究借助线粒体数据（mitochondrial data）、新纳入的类群以及多组外部校准点（external calibration points），估算物种形成与杂交过程的演化时间，并检验新几内亚周边古岛的Kalyptatherina属、苏拉威西西南部的Marosatherina属与马拉利湖类群之间的系统地理关系。 Results: 与此前预期相悖，Kalyptatherina属是马拉利湖旗银汉鱼科的最近缘类群，而Marosatherina属为该演化支（clade）的姊妹群。针对苏拉威西的古地理重建（palaeogeographic reconstructions）表明，马拉利湖辐射类群与Kalyptatherina属的近缘关系可通过“地体漂移（terrane-rafting）”情景解释，而原始Marosatherina属或通过海洋扩散途径定居苏拉威西。本研究最可靠的分析结果显示，马塔诺湖两大特有演化支的分化起始时间约为190万年；两类支系内部的多样化过程明显更晚（约100万年）；尖鳍型类群中检出的河流单倍型（haplotype）起源时间更晚（约40万年）。 Conclusions: 苏拉威西的旗银汉鱼科极有可能起源于萨胡尔陆架（Sahul Shelf）区域，通过海洋扩散与岛屿/地体漂移两种途径抵达该岛，并从河流生境入侵马拉利湖系。马塔诺湖底栖（epibenthic）尖鳍型与主要营中上层至底中层（benthopelagic）生活的圆鳍型之间的分化时间估算值，与该裂谷湖（rift lake）的地质年代估算结果高度吻合。两类演化支内部的多样化过程明显早于与河流种群的杂交事件。针对马塔诺湖的研究结果支持如下演化情景：河流种群入侵湖泊后，首先发生底栖-中上层生态位分化，随后两类演化支在过去100万年内快速辐射演化；河流种群与尖鳍型的二次杂交发生时间更晚，因此极有可能并未参与该底栖类群集群的初始分化过程。