Experimental paleoecology (resurrection ecology): Chasing Van Valen's Red Queen hypothesis

Abstract

Taking an experimental approach to paleoecology, we evaluated the prey portion of Van Valen's Red Queen hypothesis by retrieving diapausing eggs from lake sediments for laboratory tests of evolutionary responses. The sediments consisted of core samples from Portage Lake (Michigan), which were dated by a combination of varve counts and radioisotope ( 137 Cs and 210 Pb) techniques. The sedimentary record of Portage Lake documented several major environmental changes (mining, channeling, post-1950s eutrophication) over the past century. Remains of Leptodora, Chaoborus, and Polyphemus from sediments and historic fish surveys suggested a changing balance of invertebrate and vertebrate (fish) predators. Daphnia retrocurva was present in Portage Lake for over 80 yr and replaced Daphnia dentifera during the eutrophication period. Against the background of environmental change, we tested a part of the Red Queen hypothesis (i.e., that the prey species D. retrocurva must be continually evolving relative to its primary invertebrate predator, just to remain in place). We examined D. retrocurva morphology and genetics through time by retrieving and hatching diapausing eggs from different sediment strata for genetic characterization and by common garden experiments (i.e., isolates reared under the same environmental conditions). Mitochondrial DNA 12S/16S analyses and allozyme electrophoresis were used to characterize hatchlings from various levels. Allele frequencies at one allozyme (Pgi) locus in D. retrocurva differed over the eutrophication phase, suggesting founder effects, natural selection, or both. Common garden experiments with D. retrocurva hatchlings documented significant microevolutionary adjustments in both helmet and spine lengths, supporting the hypothesis of continual evolution in prey against a changing balance of predation.

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

“…The occurrence of eutrophication processes are well known to be associated with reduced biodiversity and water quality, but the evolutionary consequences for species are largely unexplored (13). Our study associates rapid ecological changes in lakes with the evolutionary fate and genetic consequences of hybridization and introgression covering a time period of nearly 100 years.…”

“…Therefore, abundances of resting eggs over time do not necessarily represent the short-term success or fitness of taxa or clonal lineages at a given time period (11,12). Instead, relative abundances of taxa or genotypes derived from resting egg banks reveal information about lineages that successfully contributed genes to the next generation (13). Thus, analyses of resting egg banks allow one to trace the long-term evolutionary fate of lineages (7,8,13).…”

“…Instead, relative abundances of taxa or genotypes derived from resting egg banks reveal information about lineages that successfully contributed genes to the next generation (13). Thus, analyses of resting egg banks allow one to trace the long-term evolutionary fate of lineages (7,8,13). Although sediment remains have been used to assess the species compositional changes in association with eutrophication (14,15), hardly anything is known about changes in the molecular genetic composition of populations during a period of rapid anthropogenic changes and subsequent recovery.…”

Hundred years of genetic structure in a sediment revived diatom population

“…Ecologically marginal environments accommodate populations that experience extreme selection regimes and contain individuals that are genetically impoverished (33). The occurrence of eutrophication processes is known to be associated with reduced diversity (34) and serves as an explanation here, because Mariager Fjord is hypertrophic. Increased frequency of asexual reproduction reduces genetic variation, and among facultative asexual species, populations living in marginal environments tend to reproduce asexually to a large extent (35,36).…”

Ecological genomics in Daphnia: stress responses and environmental sex determination

“…A powerful tool for microevolutionary studies is the hatching of dormant diapause embryos from sediment core samples of ponds and lakes, dubbed 'resurrection ecology' (Kerfoot and Weider, 2004). Implications of migration through time, or the effects of overlapping generations on population dynamics, are an active research area (for example, Cáceres and Tessier, 2004).…”