Differences in life-histories refute ecological equivalence of cryptic species and provide clues to the origin of bathyal Halomonhystera (Nematoda).
The discovery of morphologically very similar but genetically distinct species complicates a proper understanding of the link between biodiversity and ecosystem functioning. Cryptic species have been frequently observed to co-occur and are thus expected to be ecological equivalent. The marine nematode Halomonhystera disjuncta contains five cryptic species (GD1-5) that co-occur in the Westerschelde estuary. In this study, we investigated the effect of three abiotic factors (salinity, temperature and sulphide) on life-history traits of three cryptic H. disjuncta species (GD1-3). Our results show that temperature had the most profound influence on all life-cycle parameters compared to a smaller effect of salinity. Life-history traits of closely related cryptic species were differentially affected by temperature, salinity and presence of sulphides which shows that cryptic H. disjuncta species are not ecologically equivalent. Our results further revealed that GD1 had the highest tolerance to a combination of sulphides, high salinities and low temperatures. The close phylogenetic position of GD1 to Halomonhystera hermesi, the dominant species in sulphidic sediments of the Håkon Mosby mud volcano (Barent Sea, 1280 m depth), indicates that both species share a recent common ancestor. Differential life-history responses to environmental changes among cryptic species may have crucial consequences for our perception on ecosystem functioning and coexistence of cryptic species.
Biology Department, Research Group Marine Biology, Ghent University, Ghent, Belgium; Center for Molecular Phylogenetics and Evolution (CeMoFe), Ghent University, Ghent, Belgium.
Jelle
J
Van Campenhout
Biology Department, Research Group Marine Biology, Ghent University, Ghent, Belgium; Center for Molecular Phylogenetics and Evolution (CeMoFe), Ghent University, Ghent, Belgium.
Sofie
S
Derycke
Biology Department, Research Group Marine Biology, Ghent University, Ghent, Belgium; Center for Molecular Phylogenetics and Evolution (CeMoFe), Ghent University, Ghent, Belgium.
Tom
T
Moens
Biology Department, Research Group Marine Biology, Ghent University, Ghent, Belgium.
Ann
A
Vanreusel
D000818:Animals; D055669:Ecological and Environmental Phenomena; D019143:Evolution, Molecular; D005260:Female; D008018:Life Cycle Stages / Q000187:drug effects; D008297:Male; D009348:Nematoda / Q000196:embryology / Q000254:growth & development*; D010058:Oviposition / Q000187:drug effects; D010063:Ovum / Q000502:physiology; D010802:Phylogeny; D054712:Salinity; D013440:Sulfides / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors
D013440:Sulfides