The impact of human-made ecological changes on the genetic architecture of Daphnia species

Abstract

The overenrichment (eutrophication) of aquatic ecosystems with nutrients leading to algal blooms and anoxic conditions has been a persistent and widespread environmental problem. Although there are many studies on the ecological impact of elevated phosphorus (P) levels (e.g., decrease in biodiversity and water quality), little is known about the evolutionary consequences for animal species. We reconstructed the genetic architecture of a Daphnia species complex in 2 European lakes using diapausing eggs that were isolated from sediment layers covering the past 100 years. Changes in total P were clearly associated with a shift in species composition and the population structure of evolutionary lineages. Although environmental conditions were largely reestablished after peak eutrophication during the 1970s and 1980s, original species composition and the genetic architecture of species were not restored but evolved along new evolutionary trajectories. Our data demonstrate that anthropogenically induced temporal alterations of habitats are associated with long-lasting changes in communities and species via interspecific hybridization and introgression.biological archive ͉ eutrophication ͉ hybridization ͉ introgression ͉ invasiveness

Modes and mechanisms of aDaphniainvasion

“…As a result, not only is D. galeata able to invade Swiss lakes after they are eutrophied, this taxon is unable to persist after a lake has experienced reoligotrophication, whereas D. longispina survives under both conditions. This pattern provides a mechanistic underpinning for the palaeogenetic patterns observed in several lakes north of the Alps: the appearance of either D. galeata clones or its genes in D. galeata  D. longispina hybrids as primary productivity increased and their subsequent decline following nutrient reduction owing to governmental regulation of wastewater inputs [14,15].…”

“…Both species live in Greifensee [14,18], but no clone from Greifensee was used in the experiment to minimize the chance of any local environment by the clone effect. The experiment comprised a full factorial design with two temperatures (168C and 228C) and two food conditions.…”

“…Among the ecologically most important freshwater taxa responding to environmental change are members of the genus Daphnia [11,12], which in many lakes are critical species in the pelagic food chain [13]. Recently, Brede et al [14] and Rellstab et al [15] proposed that the changes during the past half century in the geographical distribution of Daphnia galeata in central Europe represent invasion success as Lake Constance and other unproductive lakes in Switzerland became eutrophied by nutrient pollution that accompanied population and economic growth following World War II [16]. Using molecular genetic analyses of diapausing eggs isolated from dated lake sediments, these authors showed that genes diagnostic of D. galeata first appeared in the 1950s when phosphorus (P) concentrations began to increase.…”

Hundred years of genetic structure in a sediment revived diatom population

“…Diapausing eggs produced by the water flea Daphnia are an exception. Subfossil resting eggs, often viable for up to 100 y and containing sufficient quality DNA for genetic analysis (5), have permitted studies of the effects of eutrophication on genetic structure that are important for the ecology and evolution of freshwater bodies (6). However, there are no equivalent studies in the marine environment, and the effects of environmental changes on intraspecific genetic structure and microevolution of eukaryote protists are poorly understood.…”

An experimental test of the ability of Daphnia galeata resting egg production in Lake Biwa

“…Jankowski and Straile (2003) suggested that eutrophication may cause a decreased sexual reproduction in Daphnia species through, for example, changes in the genetic structure of the populations (Brede et al, 2009). In addition, Shurin and Dodson (1997) and Dodson et al (1999aDodson et al ( , 1999b showed that anthropogenic perturbations, such as endocrine disrupter contamination, can inhibit sexual reproduction of Daphnia species.…”