Abstract
The existence of multiple independently derived populations in landlocked marine lakes provides an opportunity for fundamental research into the role of isolation in population divergence and speciation in marine taxa. Marine lakes are landlocked water bodies that maintain a marine character through narrow submarine connections to the sea and could be regarded as the marine equivalents of terrestrial islands. The sponge Suberites diversicolor (Porifera: Demospongiae: Suberitidae) is typical of marine lake habitats in the Indo-Australian Archipelago. Four molecular markers (two mitochondrial and two nuclear) were employed to study genetic structure of populations within and between marine lakes in Indonesia and three coastal locations in Indonesia, Singapore and Australia. Within populations of S. diversicolor two strongly divergent lineages (A & B) (COI: p = 0.4% and ITS: p = 7.3%) were found, that may constitute cryptic species. Lineage A only occurred in Kakaban lake (East Kalimantan), while lineage B was present in all sampled populations. Within lineage B, we found low levels of genetic diversity in lakes, though there was spatial genetic population structuring. The Australian population is genetically differentiated from the Indonesian populations. Within Indonesia we did not record an East-West barrier, which has frequently been reported for other marine invertebrates. Kakaban lake is the largest and most isolated marine lake in Indonesia and contains the highest genetic diversity with genetic variants not observed elsewhere. Kakaban lake may be an area where multiple putative refugia populations have come into secondary contact, resulting in high levels of genetic diversity and a high number of endemic species.
Highlights
It has long been hypothesized that marine species have large geographic ranges with large population sizes, and are faced with weaker barriers to dispersal than terrestrial organisms, resulting in relatively slow rates of speciation (e.g. [1])
The existence of multiple independently derived populations in landlocked marine lakes provides an opportunity for fundamental research into the role of isolation in population divergence and speciation in marine taxa [11]
Marine lakes are anchialine systems, which are landlocked water bodies that maintain a marine character through narrow submarine connections to the sea (Fig. 1; [12])
Summary
It has long been hypothesized that marine species have large geographic ranges with large population sizes, and are faced with weaker barriers to dispersal than terrestrial organisms, resulting in relatively slow rates of speciation (e.g. [1]). Recent phylogeographic and population genetic studies on marine taxa portray a situation of ecologically heterogeneous environments on small spatial scales with several morphologically cryptic species instead of cosmopolitan species The marine lakes share many characteristics with island systems [13]: they are well-defined geographically [14,15,16], harbor unique biota with high endemism and/or an abundance of species rare that are elsewhere [16,17,18,19,20,21], and isolated populations [11,22,23]. In the present study our overall aim was to obtain insight into the role of isolation on the genetic diversity of marine lake populations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
