Generalist parasites persist in degraded environments: a lesson learned from microsporidian diversity in amphipods

Abstract

The present study provides new insight into suitable microsporidian–host associations. It relates regional and continental-wide host specialization in microsporidians infecting amphipods to degraded and recovering habitats across 2 German river catchments. It provides a unique opportunity to infer the persistence of parasites following anthropogenic disturbance and their establishment in restored rivers. Amphipods were collected in 31 sampling sites with differing degradation and restoration gradients. Specimens were morphologically (hosts) and molecularly identified (host and parasites). Amphipod diversity and abundance, microsporidian diversity, host phylogenetic specificity and continental-wide β-specificity were investigated and related to each other and/or environmental variables. Fourteen microsporidian molecular operational taxonomic units (MOTUs), mainly generalist parasites, infecting 6 amphipod MOTUs were detected, expanding the current knowledge on the host range by 17 interactions. There was no difference in microsporidian diversity and host specificity among restored and near-natural streams (Boye) or between those located in urban and rural areas (Kinzig). Similarly, microsporidian diversity was generally not influenced by water parameters. In the Boye catchment, host densities did not influence microsporidian MOTU richness across restored and near-natural sites. High host turnover across the geographical range suggests that neither environmental conditions nor host diversity plays a significant role in the establishment into restored areas. Host diversity and environmental parameters do not indicate the persistence and dispersal of phylogenetic host generalist microsporidians in environments that experienced anthropogenic disturbance. Instead, these might depend on more complex mechanisms such as the production of resistant spores, host switching and host dispersal acting individually or conjointly.

Keywords: Anthropogenic disturbance; DNA barcoding; habitat degradation; habitat restoration; host specialization; microsporidia; phylogenetic specificity; β-specificity.

Graphical abstract

Fig. 1.

Map showing sampling sites located in the (A) Boye and (B) Kinzig catchments (map created with QGIS v3.16.9).

Fig. 2.

Maximum likelihood phylogenetic tree obtained with IQ-Tree 2.0 (Minh et al., 2020) using a TIM3 + F + G4 substitution model and based on partial small ribosomal subunit rDNA data (Supplementary file 2: Dataset S1). Labels with accession number are parasite sequences retrieved from GenBank. The name of described species and reviewed sequences are marked with asterisks. Bootstrap values (1000 replicates) are indicated in green. Outgroup is indicated in purple.

Fig. 3.

Number of observed microsporidian MOTUs across sampling sites in the Boye and Kinzig catchments.