Data from: Predictive mapping to identify refuges for plant communities threatened by earthworm invasion

1. Biological invasions by cryptic ecosystem engineers can alter the
ecological and socio-economic values of ecosystems in ways that may take
decades to detect. The invasion of North American glacial refuges by
non-native earthworms offers a prominent but understudied example of a
cryptic invasion. Non-native earthworms are known to alter carbon
sequestration, disrupt mycorrhizal networks, and homogenize plant
communities, but natural resource managers still lack robust protocols to
identify and safeguard high conservation value communities (HCVCs) from
such invasions. In the absence of such protocols, or reliable methods to
eradicate non-native earthworm populations once established, there is an
urgent need for methods to identify HCVCs at risk of or potentially
shielded from earthworm invasion by the existence of abiotic barriers to
their dispersal or persistence in such sites. 2. We developed species
distribution models (SDMs) using in-situ field surveys and remotely sensed
data to (1) identify factors limiting the occurrence of non-native
Lumbricus earthworms in imperiled coastal Douglas-fir (Pseudotsuga
menziesii) forest and Garry oak (Quercus garryana) and maritime meadow
ecosystems endemic to glacial refugia of the Pacific Northwest of North
America to (2) evaluate their influence on plant species diversity and
identify abiotic factors capable of preventing their dispersal or
persistence at a site. 3. As predicted, shallow, drier soils, and steeper
terrain limited earthworm occurrence and abundance in our highly
heterogeneous study area, and earthworm presence appeared to reduce plant
species richness. Our results indicated that HCVCs endemic to shallow-soil
(<12 ± 3 cm) sites that experience regular summer drought appear to
act as refuges from invasion by non-native earthworms. Our results also
elevate concerns for the conservation of deep-soil habitats not isolated
from earthworm invasions by shallow soil, saltwater, or other barriers to
earthworm dispersal. 4. The SDMs developed here offer guidance to the
identification of potential refuges for the conservation of imperiled
native species and communities from the detrimental effects non-native
earthworms in glacial refugia of western North America, and should thereby
facilitate proactive planning by conservation practitioners.