Nuclear DNA recapitulates the cryptic mitochondrial lineages ofLumbricus rubellusand suggests the existence of cryptic species in an ecotoxological soil sentinel

Abstract

Mitochondrial DNA analysis has revealed two distinct phylogenetic lineages within the ecotoxological sentinel earthworm model Lumbricus rubellus Hoffmeister, 1843. The existence of these lineages could complicate ecotoxicological studies that use the species as a sentinel for soil contamination testing, as they may respond differently to contamination; however, as mitochondrial haplotypes are not always expected to segregate in the same way as chromosomal DNA in natural populations, we further investigated this issue by using nuclear DNA markers (microsatellites) to measure genetic diversity, differentiation, and gene flow in sympatric populations of the two L. rubellus lineages at two sites in South Wales. Our results show that sympatric populations of the two lineages are more genetically differentiated than geographically distant populations of the same lineage, and Bayesian clustering analysis revealed no evidence of gene flow between the lineages at either site. Additionally, DNA sequencing of these microsatellite loci uncovered substantial differentiation between lineages at homologous flanking regions. Overall our findings indicate a high degree of nuclear genetic differentiation between the two lineages of L. rubellus, implying reproductive isolation at the two study sites and therefore the potential existence of cryptic species. The existence of two cryptic taxa has major implications for the application of L. rubellus as an ecotoxicological sentinel. It may therefore be necessary to consider the lineages as separate taxa during future ecotoxicological studies.

The worm has turned: Behavioural drivers of reproductive isolation between cryptic lineages

“…The subtle intraspecific genetic variation shown within this species has been previously documented by King et al (2008) and Andre et al (2010) and our sequences clustered together with the described lineages A and B in these previous studies. Donnelly et al (2013) confirmed the lack of gene flow between these two lineages using microsatellite markers. Although RAD-Seq analyses revealed that certain European L. rubellus lineages may not be reproductively isolated (Giska et al, 2015), a similar genetic analysis observed that no hybridization occurs between A and B lineages in a number of UK locations where the lineages co-existed (Anderson pers.…”

Invasive lumbricid earthworms in North America—Different life histories but common dispersal?

“…This study shows that northern North American populations of the two earthworm species L. rubellus and L. terrestris share the same genetic lineages with populations of their native range in Europe. However, genetic diversity is lower in North America than in Europe, which is typical for invasive species (Sakai et al, ; Allendorf & Lundquist, ; King, Tibble, & Symondson, ; Gailing et al, ; Donnelly et al, ; Donnelly, Harper, Morgan, Pinto‐Juma, & Bruford, ; Giska et al, ). Consistent with studies in Europe, genetic diversity in L. rubellus was higher than in L. terrestris (King et al, 2008; Martinsson & Erséus, ), and intraspecific genetic distances of COI were comparable with those reported from Europe (King et al, 2008; James et al, ; Klarica, Kloss‐Brandstätter, Traugott, & Juen, ).…”

Local coexistence and genetic isolation of three pollinator species on the same fig tree species

“…Naughton et al (2014) found that microsatellite data support mtDNA lineages in Cenolia feather stars, although introgression was observed in a small number of individuals. In addition, Donnelly et al (2013) demonstrated support for mtDNA species in Lumbricus rubellus earthworms in South Wales. Interestingly though, divergent L. rubellus mtDNA lineages in Poland are not reproductively isolated (Giska et al, 2015).…”