Publications (11)33.28 Total impact
-
Article: Alien invasion in Wallace's Dreamponds: records of the hybridogenic "flowerhorn" cichlid in Lake Matano, with an annotated checklist of fish species introduced to the Malili Lakes system in Sulawesi
[show abstract] [hide abstract]
ABSTRACT: Invasive fish species can have major impacts on freshwater faunas, particularly in isolated systems harbouring adaptive animal radiations. Here, we report on the occurrence and recent rapid expansion of the hybridogenic "flowerhorn" cichlid in ancient Lake Matano, the hydrological head of the Malili Lakes system in Central Sulawesi, Indonesia. We show that flowerhorns rapidly dispersed along the lake's shoreline, inhabited most of the southern inshore habitats in 2010, and were present all around the lake in mid-2012. In addition, we present stomach content and observational data supporting the hypothesis that this cichlid threatens the local fauna through both predation and competition. We discuss 13 additional alien fish species recorded in the Malili Lakes drainage since 2000, including the recent, first record of the invasive sailfin catfish Pterygoplichthys pardalis for Sulawesi, highlighting the multitude of artificial introductions of foreign fish species into these unique and highly isolated freshwater systems. We conclude that alien fish species pose both serious and diverse threats to the fauna of the Malili Lakes system – an ecosystem of high socio-economic importance and an exceptional natural laboratory for study of evolution, referred to as "Wallace's Dreamponds". Finally, we provide recommendations for minimizing future alien species introductions.Aquatic Invasions 11/2012; 7(4). -
Article: Comparative feeding ecology of invasive Ponto-Caspian gobies
[show abstract] [hide abstract]
ABSTRACT: Invasions of Ponto-Caspian gobiid fishes are suspected to cause regime shifts in freshwater ecosystems. This study compared the trophic niche differentiations of Neogobius melanostomus and Pon-ticola kessleri in the upper Danube River using stable isotope analyses (d 13 C and d 15 N), gut content analyses and morphometric analyses of the digestive tract. Both species were identified as predacious omnivores with high dietary overlap and a generalistic feeding strat-egy. Amphipods (especially invasive Dikerogamma-rus spp.) contributed 2/3 to the index of food importance. d 15 N-signatures of N. melanostomus revealed an ontogenetic diet shift and significantly exceeded those in P. kessleri by *1.5%, indicating a niche separation of half a trophic level. P. kessleri had shorter uncoiled intestinal tracts than N. melanosto-mus, indicating a narrower niche and adaptation to animal food. Trophic niches in both species expanded during the growth period with increasing intraguild predation and cannibalism in P. kessleri and increas-ing molluscivory in N. melanostomus. P. kessleri showed a higher degree of specialization and more stable feeding patterns across seasons, whereas N. melanostomus adapted its diet according to the natural prey availability. The feeding patterns of both species observed in the upper Danube River strongly differ from those in their native ranges, underlining their great plasticity. Both goby species consumed mainly other non-native species (*92% of gut contents) and seemed to benefit from previous inva-sions of prey species like Dikerogammarus villosus. The invasive success of gobies and their prey mirror fundamental ecological changes in large European freshwater ecosystems.Hydrobiologia 09/2012; · 1.78 Impact Factor -
Article: Phenotypic traits meet patterns of resource use in the radiation of “sharpfin” sailfin silverside fish in Lake Matano
[show abstract] [hide abstract]
ABSTRACT: Disruptive natural selection on traits related to resource exploitation may lead to differential adaptation and finally to speciation. Trait utility, the performance of traits in terms of fitness, is a central criterion for the recognition of adaptive radiation. Utility of morphological structures involved in foraging can be detected by relating their variation to individual resource use. Here, we test for trophic adaptations in the radiation of “sharpfin” sailfin silversides (Atheriniformes: Telmatherinidae), endemic to ancient graben-lake Matano in central Sulawesi (Indonesia). This small species-flock is characterized by high phenotypic diversity, including traits most likely related to feeding ecology. Previous analyses suggest that species boundaries are porous, indicating very recent or possibly ongoing processes of species flock formation. To test for adaptation to resource use in this radiation, we compared morphological traits among trophic groups of individuals as identified by stomach content analyses. We analyzed variation in candidate structures or structural complexes commonly recognized as indicative of trophic adaptation in fish radiations, including shapes of body, oral and pharyngeal jaws, gill rakers and body size. We found fine-scaled morphological differentiation according to feeding habits, covering all traits analyzed. Fish-, shrimp- and egg-feeders were most distinct, with major axes of morphological variation fitting patterns of adaptation reported from other lacustrine fish radiations. Thus, the present results are consistent with fine-scaled morphological adaptation to resource use, supporting the adaptive character of the sharpfin sailfin silverside radiation. KeywordsSpeciation-Natural selection-Malili Lakes system-Geometric morphometrics-Feeding apparatus-TelmatherinidaeEvolutionary Ecology 04/2012; 24(5):957-974. · 2.45 Impact Factor -
Article: Alternative egg-feeding tactics in Telmatherina sarasinorum, a trophic specialist of Lake Matano’s evolving sailfin silversides fish radiation
[show abstract] [hide abstract]
ABSTRACT: Feeding specialisation is a typical feature of adaptive animal radiations. Different kinds of feeding specialisations have evolved in the endemic sailfin silversides species flock in Lake Matano (Central Sulawesi, Indonesia), including egg-feeding. The present study focuses on Telmatherina sarasinorum, a sailfin silverside species feeding on the eggs of related Telmatherina antoniae. Stomach content analyses supported T. antoniae eggs to be the dominant food item, independent of daytime. We hypothesized that the egg-feeders use alternative tactics for maximising egg consumption under varying densities of both, spawning T. antoniae pairs and competing conspecific egg-feeders. Focal behavioural observations were applied to describe different feeding tactics and to analyse feeding success and the related costs in terms of competitive interactions. Egg-feeders followed single courting pairs of T. antoniae or, alternatively, they switched between different spawning pairs. Following-behaviour, covering one or more spawning events of the host species, was positively related to enhanced egg consumption. Compared to feeding by switching frequently among different spawning pairs, the following tactic came at the cost of likewise increased competition. Behavioural observations suggest that some males monopolize courting pairs of T. antoniae and gain increased amounts of eggs compared to others avoiding competition by switching among pairs. The present results confirm that egg-feeding is a distinct trophic specialisation in T. sarasinorum and increase the scale of behavioural specialisation in Lake Matano’s evolving Telmatherina radiation.Hydrobiologia 04/2012; 693(1):131-139. · 1.78 Impact Factor -
Article: Time and origin of cichlid colonization of the lower Congo rapids.
[show abstract] [hide abstract]
ABSTRACT: Most freshwater diversity is arguably located in networks of rivers and streams, but, in contrast to lacustrine systems riverine radiations, are largely understudied. The extensive rapids of the lower Congo River is one of the few river stretches inhabited by a locally endemic cichlid species flock as well as several species pairs, for which we provide evidence that they have radiated in situ. We use more that 2,000 AFLP markers as well as multilocus sequence datasets to reconstruct their origin, phylogenetic history, as well as the timing of colonization and speciation of two Lower Congo cichlid genera, Steatocranus and Nanochromis. Based on a representative taxon sampling and well resolved phylogenetic hypotheses we demonstrate that a high level of riverine diversity originated in the lower Congo within about 5 mya, which is concordant with age estimates for the hydrological origin of the modern lower Congo River. A spatial genetic structure is present in all widely distributed lineages corresponding to a trisection of the lower Congo River into major biogeographic areas, each with locally endemic species assemblages. With the present study, we provide a phylogenetic framework for a complex system that may serve as a link between African riverine cichlid diversity and the megadiverse cichlid radiations of the East African lakes. Beyond this we give for the first time a biologically estimated age for the origin of the lower Congo River rapids, one of the most extreme freshwater habitats on earth.PLoS ONE 01/2011; 6(7):e22380. · 4.09 Impact Factor -
Article: Not a simple case - A first comprehensive phylogenetic hypothesis for the Midas cichlid complex in Nicaragua (Teleostei: Cichlidae: Amphilophus).
[show abstract] [hide abstract]
ABSTRACT: Nicaraguan Midas cichlids from crater lakes have recently attracted attention as potential model systems for speciation research, but no attempt has been made to comprehensively reconstruct phylogenetic relationships of this highly diverse and recently evolved species complex. We present a first AFLP (2793 loci) and mtDNA based phylogenetic hypothesis including all described and several undescribed species from six crater lakes (Apoyeque, Apoyo, Asososca Leon, Masaya, Tiscapa and Xiloá), the two great Lakes Managua and Nicaragua and the San Juan River. Our analyses demonstrate that the relationships between the Midas cichlid members are complex, and that phylogenetic information from different markers and methods do not always yield congruent results. Nevertheless, monophyly support for crater lake assemblages from Lakes Apoyeque, Apoyo, A. Leon is high as compared to those from L. Xiloá indicating occurrence of sympatric speciation. Further, we demonstrate that a 'three species' concept for the Midas cichlid complex is inapplicable and consequently that an individualized and voucher based approach in speciation research of the Midas cichlid complex is necessary at least as long as there is no comprehensive revision of the species complex available.Molecular Phylogenetics and Evolution 09/2010; 56(3):1011-24. · 3.61 Impact Factor -
Article: Gene flow at the margin of Lake Matano’s adaptive sailfin silverside radiation: Telmatherinidae of River Petea in Sulawesi
[show abstract] [hide abstract]
ABSTRACT: Classical speciation concepts focus almost exclusively on the evolution of strict reproductive isolation as a prerequisite for speciation. However, there is a growing body of evidence indicating that speciation is possible despite or even triggered by gene flow among populations or species. Previous findings indicate that introgressive hybridization is a dominant phenomenon in the adaptive radiation of sailfin silversides (Telmatherinidae) endemic to Lake Matano (Sulawesi). In this study, we investigate patterns of genotypic and phenotypic variation of “sharpfin” sailfin silversides in the outlet area of L. Matano and six locations along River Petea, which is the only connection between L. Matano and other lakes and streams of the Malili Lakes system. Fieldwork revealed no hints for a previously cited major waterfall in River Petea, which was thought to separate L. Matano’s sailfin silverside radiation from the diversity of the downstream lake drainages. Likewise, genomic (AFLP) and morphometric data suggest high levels of gene flow between upper and lower stretches of this river, as well as between riverine Petea and lacustrine Matano populations. Increasing levels of genotypic and phenotypic dissimilarity are correlated with distance over a remarkably short geographic range.Hydrobiologia 11/2008; 615(1):201-213. · 1.78 Impact Factor -
Article: Age and spread of the haplochromine cichlid fishes in Africa
[show abstract] [hide abstract]
ABSTRACT: a b s t r a c t The Haplochromini are by far the most species-rich cichlid fish tribe that originated along with the so-called primary radiation of the Lake Tanganyika cichlid species flock, i.e. at the same time during which the majority of the endemic Lake Tanganyika cichlid tribes emerged. Unlike the other tribes, the haplo-chromines are not restricted to Lake Tanganyika but distributed throughout Africa, except for the north-western part of the continent. Haplochromine cichlids seeded the adaptive radiation of cichlid fishes in Lakes Malawi, Kivu, Victoria, Turkana, as well as in the now extinct paleo-Lake Makgadikgadi. Here we present a comprehensive phylogenetic and phylogeographic analysis of haplochromine cichlids that is based upon DNA sequences of two mitochondrial gene segments of riverine taxa covering all major Afri-can biogeographic regions where haplochromines are found. Our analysis revealed that six lineages of haplochromines originated within a short period of time, about 5.3–4.4 MYA. These haplochromine lin-eages show a highly complex phylogeographic pattern, probably severely influenced by climate-and/or geology-induced changes of the environment, with river capture events most likely playing an important role for species dispersal.Molecular Phylogenetics and Evolution 10/2008; 49(1):153-169. · 3.61 Impact Factor -
Article: Adaptive sympatric speciation of polychromatic "roundfin" sailfin silverside fish in Lake Matano (Sulawesi).
[show abstract] [hide abstract]
ABSTRACT: The significance of sympatric speciation is one of the most controversial topics in evolutionary biology. Theory suggests that different factors can lead to speciation in full geographical contact, including selection and nonrandom mating. Strict criteria have been established for assessing sympatric speciation, which have been met in only a very few cases. Here, we investigate differentiation among sympatric morphospecies and color morphs of "roundfin" sailfin silversides (Telmatherinidae), small freshwater fish endemic to ancient Lake Matano in Central Sulawesi (Indonesia). Morphospecies are distinct according to body shape (geometric morphometrics), population structure (population-level amplified fragment length polymorphism [AFLP] markers), ecology, and mating behavior (habitat transects, stomach contents). Explorative genome scans based on AFLPs indicate that divergent selection affects only 1.3-4.2% of the analyzed loci, suggesting an early stage of speciation. Transect data demonstrate strong assortative mating and adaptive niche differentiation. However, we find no restrictions in gene flow among the conspicuous male color morphs. In summary, our data are consistent with a sympatric mode of divergence among three morphospecies under conditions effectively ruling out allopatric scenarios. Substantial, but incomplete, reproductive isolation suggests an early stage of speciation, most likely due to ecological selection pressure.Evolution 07/2008; 62(9):2178-95. · 5.15 Impact Factor -
Article: Age and spread of the haplochromine cichlid fishes in Africa.
[show abstract] [hide abstract]
ABSTRACT: The Haplochromini are by far the most species-rich cichlid fish tribe that originated along with the so-called primary radiation of the Lake Tanganyika cichlid species flock, i.e. at the same time during which the majority of the endemic Lake Tanganyika cichlid tribes emerged. Unlike the other tribes, the haplochromines are not restricted to Lake Tanganyika but distributed throughout Africa, except for the northwestern part of the continent. Haplochromine cichlids seeded the adaptive radiation of cichlid fishes in Lakes Malawi, Kivu, Victoria, Turkana, as well as in the now extinct paleo-Lake Makgadikgadi. Here we present a comprehensive phylogenetic and phylogeographic analysis of haplochromine cichlids that is based upon DNA sequences of two mitochondrial gene segments of riverine taxa covering all major African biogeographic regions where haplochromines are found. Our analysis revealed that six lineages of haplochromines originated within a short period of time, about 5.3-4.4 MYA. These haplochromine lineages show a highly complex phylogeographic pattern, probably severely influenced by climate- and/or geology-induced changes of the environment, with river capture events most likely playing an important role for species dispersal.Molecular Phylogenetics and Evolution 07/2008; 49(1):153-69. · 3.61 Impact Factor -
Article: Adaptive radiation and hybridization in Wallace's Dreamponds: evidence from sailfin silversides in the Malili Lakes of Sulawesi.
[show abstract] [hide abstract]
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.Proceedings of the Royal Society B: Biological Sciences 10/2006; 273(1598):2209-17. · 5.41 Impact Factor
Top co-authors
Top Journals
Institutions
-
2008–2012
-
Zoologische Staatssammlung München
München, Bavaria, Germany -
Zoologisches Forschungsmuseum Alexander Koenig
Bonn, North Rhine-Westphalia, Germany
-
-
2006
-
Universität Köln
- Institute for Genetics
Köln, North Rhine-Westphalia, Germany
-
