Joshua A. Mackie

Ecology of cryptic invasions: latitudinal segregation among Watersipora (Bryozoa) species

Watersipora is an invasive genus of bryozoans, easily dispersed by fouled vessels. We examined Cytochrome c oxidase subunit I haplotypes from introduced populations on the US Pacific coastline to investigate geographic segregation of species and/or haplotypes. In California, the W. subtorquata group fell into three major sub-groups: W. subtorquata clades A and B, and W. “new sp.”. W. subtorquata clades A and B were common in southern California south of Point Conception, a recognized biogeographic boundary, whereas further north, W. subtorquata clade A and W. n. sp. were frequent. The southern California region also had colonies of a morphologically distinct species, W. arcuata, also found in southern Australia and Hawaii; COI variation indicates a common ancestral source(s) in these introductions. The distribution of Watersipora-complex lineages on different coastlines is shown to be temperature correlated. Accordingly, pre-exisitng temperature-based adaptations may play a key role in determining invasion patterns.

Cryptic species in the cosmopolitan Bugula neritina complex (Bryozoa, Cheilostomata)

Previous analyses of the mitochondrial gene cytochrome c oxidase subunit 1 (COI) and γ‐proteobacterial endosymbiont diversity have suggested that the marine bryozoan Bugula neritina is a complex of three cryptic species, namely Types S, D and N. Types D and N were previously reported to have restricted distributions along California (western USA) and Delaware and Connecticut (eastern USA), respectively, whereas Type S is considered widespread in tropical, subtropical and temperate regions due to anthropogenic transport. Here, Bayesian species delimitation analysis of a data set composed of two mitochondrial (COI and large ribosomal RNA subunit [16S]) and two nuclear genes (dynein light chain roadblock type‐2 protein [DYN] and voltage‐dependent anion‐selective channel protein [VDAC]) demonstrated that Types S, D and N correspond to three biological species. This finding was significantly supported, in spite of the combinations of priors applied for ancestral population size and root age. Furthermore, COI sequences were used to assess the introduction patterns of the cosmopolitan Type S species. Two COI haplotypes of Type S (S1a and S1d) were found occurring at a global scale. Mantel tests showed correlation between these haplotypes and local sea surface temperature tolerance. Accordingly, the distributions of Type S haplotypes may reflect intraspecific temperature tolerance variation, in addition to the role of introduction vectors. Finally, we show that the Type N may also have been introduced widely, as this species was found for the first time in Central California and north‐eastern Australia.

Loss of evolutionary resistance by the oligochaete Limnodrilus hoffmeisteri to a toxic substance - cost or gene flow?

The oligochaete Limnodrilus hoffmeisteri at Foundry Cove (FC), New York evolved genetic resistance to cadmium (Cd) and lost resistance after contaminated sediments were removed by dredging. Selection (on survival time in dissolved Cd) was used to generate tolerance to evaluate fitness cost, the commonplace expectation for evolutionary reversal. The hypothesis that gene flow from neighboring populations could “swamp” resistance was addressed by 16S rDNA sequences. In disagreement with the cost hypothesis, selected‐Cd tolerant worms and controls showed no difference in total fecundity or growth rate in environments. Highly‐Cd‐tolerant worms of the FC‐selected population grew rapidly at different temperatures and showed no growth impairment in the presence of Cd, indicating metabolically efficient resistance. Genetic structure at FC was consistent with invasion of genotypes from an adjacent population in the time since dredging. Applying selection to lines from FC and a reference site, demonstrated a more rapid increase in Cd tolerance in FC‐origin lines, indicating standing allelic variation for resistance at FC (despite phenotypic erosion). The selection experiment supports the view that resistance is simply controlled—probably by one allele of large effect. Whether such rapid “readaptation” could occur naturally is an important question for understanding broad effects of pollutants.

Rapid and reliable inference of mitochondrial phylogroups among Watersipora species, an invasive group of ship-fouling species (Bryozoa, Cheilostomata).

Tracking biological invasion is an essential part of conservation, and identifying invasive species quickly following an introduction can be imperative. Invasive organisms are often difficult to distinguish visually, which can delay appropriate response measures. We have designed a multiplex-PCR system to effectively distinguish colonies of divergent cytochrome oxidase subunit 1 (COI) sequence clades in the bryozoan genus Watersipora, a genus with invasive species which are aggressive foulers of ship hulls, to understand small-scale invasion patterns and the ecology of lineages of different geographic origins. The identification of previously defined COI lineage groups is conducted using PCR reactions containing five primers. Lineage-specific fragment lengths were produced with 100% reliability, suggesting the assay will offer a rapid and economical means of studying invasion dynamics and the role of adaptation in this rapidly invading species complex.

High-throughput Illumina sequencing and microsatellite design in Watersipora (Bryozoa), a complex of invasive species.

The bryozoan genus Watersipora includes rapidly invading species that are becoming common globally. We used paired-end Illumina sequencing to identify thousands of potentially amplifiable microsatellite loci, enabling researchers to track patterns of the invasive spread, and to facilitate ecological and evolutionary question setting. We describe variability of nine loci within recently introduced populations of two Watersipora species in California.