Adaptive radiation and hybridization in Wallace's Dreamponds: evidence from sailfin silversides in the Malili Lakes of Sulawesi

Abstract

Adaptive radiations are extremely useful to understand factors driving speciation. A challenge in speciation research is to distinguish forces creating novelties and those relevant to divergence and adaptation. Recently, hybridization has regained major interest as a potential force leading to functional novelty and to the genesis of new species. Here, we show that introgressive hybridization is a prominent phenomenon in the radiation of sailfin silversides (Teleostei: Atheriniformes: Telmatherinidae) inhabiting the ancient Malili Lakes of Sulawesi, correlating conspicuously with patterns of increased diversity. We found the most diverse lacustrine species-group of the radiation to be heavily introgressed by genotypes originating from streams of the lake system, an effect that has masked the primary phylogenetic pattern of the flock. We conclude that hybridization could have acted as a key factor in the generation of the flock's spectacular diversity. To our knowledge, this is the first empirical evidence for massive reticulate evolution within a complex animal radiation.

DNA Barcoding Indonesian freshwater fishes: challenges and prospects

“…In agreement with morphology and nuclear data, mitochondrial markers resolved major lineages of the radiation [41], and provided valuable insights into the phylogenetic history, the origin, and time estimates of its divergence [77]. Mitochondrial sequences, however, are less suited for discriminating morphospecies within the major lineages of this radiation [41,72]. For instance, introgressive hybridization between stream-and lake-dwelling sailfin silversides [78] has lead to severe confusion in previous studies relying solely on mitochondrial markers for species delineation [e.g.…”

“…13, [41][42][43][44][45]. The distribution of the number of species description per decade highlights that taxonomic studies have been fragmented during the pre-modern period but also that despite two centuries and a half of ichthyological inventories; many species are still described regularly throughout Indonesia, not only from the most remote rivers and lakes of Wallacea and Sahul.…”

“…The most spectacular radiation in Sulawesi is observed in the sailfin silversides (Telmatherinidae; Fig. 5) from the interconnected Malili Lakes, including the 590 m deep graben-lake Matano [41,[70][71][72]. These small, Atheriniformes fishes with colorful male ornamentation are closely related to New Guinea's and Australia's rainbowfishes, and serve as model system for the study of speciation mechanisms [summarized in 73], and the maintenance of color polymorphisms in nature [e.g.…”

“…Mitochondrial sequencing was performed as one of the initial steps for estimating sailfin silverside species diversity [41,76]. In agreement with morphology and nuclear data, mitochondrial markers resolved major lineages of the radiation [41], and provided valuable insights into the phylogenetic history, the origin, and time estimates of its divergence [77]. Mitochondrial sequences, however, are less suited for discriminating morphospecies within the major lineages of this radiation [41,72].…”

A New, Remarkably Colorful, Small Ricefish of the Genus Oryzias (Beloniformes, Adrianichthyidae) from Sulawesi, Indonesia

“…Endemism of freshwater fishes is particularly well documented among the atherinomorph orders Atheriniformes and Beloniformes. Sixteen of the 17 recognized species of the atheriniform family Telmatherinidae are endemic to Sulawesi (Saeed and Ivantsoff, 1991;Kottelat et al, 1993;Herder et al, 2006). Among beloniforms, nine of the 16 recognized species of the zenarchopterid genus Nomorhamphus (Meisner, 2001;Collette, 2004) and 13 of the 29 known Recent adrianichthyids or ricefishes, including the new species described herein (Parenti, 2008), are Sulawesi endemics.…”