The Ancient Lakes of Indonesia: Towards Integrated Research on Speciation

Abstract

Ancient lakes have provided considerable insights into the drivers of speciation and adaptive radiation in aquatic organisms. Most studies of species-flocks, however, focus only on a single group of organisms, and few have attempted to integrate geological, limnological, ecological, and genetic drivers of speciation on multiple species-flocks at various trophic levels. As such, there is a need for a comprehensive model system for research on speciation in aquatic environments where multiple radiations are investigated at various levels of biological organization (e.g., individual, population, and ecosystem) and placed in light of geographical and geological setting. The ancient Malili Lakes of Sulawesi, Indonesia, are ideal candidates for such a model, and represent the only hydrologically connected ancient lakes in the world. These lakes are characterized by ultra-oligotrophy and unique physicochemical conditions that govern the composition and production of planktonic communities. At higher trophic levels, there are three recurring trends: (1) low taxonomic richness and simple community structures, (2) adaptive radiations with trophic specialization, and (3) remarkably high endemism with evolutionary innovations throughout the lakes and species-flocks. Furthermore, the restricted geographic distributions of species-flocks within the Malili Lakes indicate that each lake constitutes a unique environment, and dispersal among lakes is limited, despite close contemporary connectivity. These observations suggest that ecological and evolutionary processes are regulated from the bottom up, and speciation is primarily facilitated by interspecific and intraspecific competition for limited resources. The Malili Lakes represent an outstanding natural model for integrative research into speciation as they offer the opportunity to explore the roles of geography, dispersal, and selection in the radiation of aquatic organisms.

Rugged adaptive landscapes shape a complex, sympatric radiation

“…1.9 Myr. This is in general agreement with the estimated geological age of the lake [20], and implies ages of approx. 1 Myr for the onset of divergence within both sharpfins and roundfins [28].…”

“…The species flock is endemic to Lake Matano [20] and consists of several ecological specialists with conspicuous morphological and behavioural adaptations to various ecological niches [21][22][23]. However, specific morphotypes do not form well-sorted clades in phylogenetic analyses based on mitochondrial markers [24].…”

Cherax quadricarinatus(von Martens) has invaded Indonesian territory west of the Wallace Line: evidences from Java

“…Although no crayfish species are native to Indonesia with the exception of West Papua and Papua Provinces, there are many unique freshwater habitats (Vaillant et al, 2011) with occurrence of endemic decapods such as shrimps (e.g. Zitzler and Cai, 2006;von Rintelen et al, 2008) and crabs (Ng, 1989;Ng et al, 2015) which can potentially be threatened by spread of non-native crayfish.…”

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

“…The endemic sailfin silversides radiation of the Malili Lakes serves as a model system in evolutionary ecology research (see [10,19,41] for reviews). The detailed and temporal reconstruction of the phylogenetic history of the Telmatherinidae is crucial for exploring the likely conditions underlying speciation processes, including the spatial origin and morphological traits of ancestral and introgressed populations.…”