Untangling the knots in the evolutionary history of Dactylogyrus (Monogenea) and their Squalius hosts (Cyprinoidei)
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| Year of publication | 2022 |
| Type | Conference abstract |
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| Description | One of the fundamentals of evolutionary biology is the study of host-parasite coevolutionary relationships. Due to the intertwined evolutionary history of two interacting species and the ongoing coadaptation processes of hosts and parasites we can expect that studying parasites will shed more light on the evolutionary processes of their hosts. Monogenea (ectoparasitic Platyhelminthes) and their fish hosts represent one of the best models for studying host-parasite evolutionary relationships using the cophylogenetic approach. These parasites developed remarkably high host specificity, where each host species often serves as a potential host for its own host-specific monogenean species. In the present study, we investigated the cophylogenetic relationships in the Dactylogyrus-Squalius system, as Squalius is one of the few cyprinoid genera inhabiting all four major peri-Mediterranean peninsulas. Since 2014, 29 endemic Squalius species were examined for the presence of Dactylogyrus parasites, and a total of 13 Dactylogyrus species were collected from the gills of 20 Squalius species at 28 localities in ten countries. To assess the evolutionary history in Dactylogyrus, four genetic markers, specifically, the partial 18S rRNA and partial 28S rRNA genes; and 5.8S and ITS1 regions were used for the phylogenetic analyses. To confirm the fish species identification and also obtain molecular data for fish hosts, the complete mitochondrial DNA cytochrome b gene was sequenced. For the cophylogenetic analyses the dual-based approach was employed: distance-based methods allowed us to calculate patristic distances for parasite and host phylogenies to assess the significance of global fit and individual coevolutionary links; and eventbased methods that allowed us to test the importance of each coevolutionary event in the host-parasite phylogenies. The phylogenetic reconstruction revealed a polyphyletic origin of Dactylogyrus species parasitizing congeneric Squalius. Based on the host specificity, these Dactylogyrus species were divided into three groups: the strict specialists parasitizing the single host species, geographic specialists parasitizing congeners in the limited geographical region, and true generalists parasitizing congeners in various geographical regions. Although the distance-based methods did not reveal statistically significant global cophylogenetic structure in the studied system, several host-parasite links among Iberian endemic species were revealed to contribute significantly to the overall structure. The highest host range, and genetic variability associated with it, were recorded in D. folkmanovae, parasitizing nine Squalius species, and D. vistulae, parasitizing 13 Squalius species. Two different dispersion mechanisms and morphological adaptations to potential fish hosts were well reflected in contrasting cophylogenetic patterns for these two generalist species in our study. While cospeciation plays the important role in diversification within D. folkmanovae with its host, D. vistulae diversification is driven mainly by the host switching. |
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