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Taxon | System | Species status | Evidence for phylogenetic sister taxa? | Divergence in parasite assemblage? | Divergence in resistance traits? | Does parasite-driven divergence precede other divergence? | Is there parasite-mediated selection against immigrants? | Is there parasite-mediated selection against hybrids? | Is there assortative mating? | Is there divergence in a potential revealing signal or MHC? | Is divergent mate choice based on a revealing signal? | Is divergent mate choice based on MHC-odours? | The geography of divergence | Refs |
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Fish | Three-spine stickleback sympatric species pairs in Vancouver lakes (Canada) | Reproductively isolated species | Yes in Paxton lake, no in Priest lake | Yes, limnetic species have much more cestodes, fewer mollusks and different trematodes | Divergence in MHC profiles | Not known | No data | No data | Yes | Yes, the limnetic species display redder male breeding dress and have lower MHC allele diversity | Yes, it is at least partly based on male breeding dress | Not tested | Reinforcement after secondary contact | [58, 91, 142] |
| Three-spine stickleback marine versus freshwater populations on Vancouver coast (Canada) | Parapatric populations, perhaps species | No data, but very likely | Not known (but likely between the Sea and freshwaters) | Freshwater residents are less susceptible than marines to infestation with freshwater parasites, the reverse is not know | Not known | Yes, selection against marine immigrants operates in freshwaters; the reciprocal direction is not known | No data | Not known | Not known | Not tested | Not tested | Parapatric | [70] |
| Three-spine stickleback marine versus freshwater species in Scotland | Parapatric populations, perhaps species | No data, but very likely | Yes, freshwater residents are heavily infested by a cestode | Freshwater residents are less susceptible than marines to infestation with freshwater parasites, the reverse is not known | Not known | Yes, selection against marine immigrants operates in freshwaters; the reciprocal direction is not known | No data | Not known | Not known | Not tested | Not tested | Parapatric | [70] |
| Three-spine stickleback parapatric lake and river populations in Schleswig Holstein (Germany) | Parapatric populations, perhaps quite old | Lake and stream populations are no direct sister taxa but belong to geographically more widespread reciprocally monophyletic clades | Yes, lake populations harbor larger numbers of parasites compared to river populations | Divergence in MHC profiles, immunological parameters and habitat specific resistance | Not known, but unlikely given the wide geographical distribution of the lake and the stream clade | Likely, river ecotypes acquire higher parasite load in lake exposure compared to lake ecotype, but no difference in reciprocal river exposure | No, intermediates do not suffer increased susceptibility to parasites | Yes | Yes, the lake population has larger MHC allele diversity | Not tested | Yes: pleiotropy: pre-existing tendency for MHC complementarity causes female discrimination against too dissimilar males, that is, assortative mating. indirect selection: female choice for locally resistant males | Parapatric | [54–56, 92] |
| Three-spine stickleback, marine versus freshwater populations in Atlantic Canada | Parapatric populations | No data | Yes, different parasite taxa are abundant in different environments | Different MHC profiles between the populations | Not known | No data | No data | Yes | Yes, different MHC allele frequencies between the populations | Not tested | Weakly so, and labile to environmental conditions | Parapatric | [57] |
| Lake Victoria cichlids Pundamilia pundamilia and Pundamilia nyererei | Complete speciation continuum, but parasites only studied at the complete speciation stage | Yes, from microsatellite and AFLP data | Yes, different parasite taxa, but data available only for the complete speciation stage in speciation continuum | No data | Not known but perhaps not likely given that other traits diverge very early in the process | No data | No data | Yes | Yes, males of P. pundamilia show bright blue coloration and males of P. nyererei show bright red coloration | Female preference for male nuptial coloration, which appears to be a revealing signal at least in one of the species | Olfaction is not required to maintain assortative mating | Geographically sympatric, ecologically parapatric | [10, 66, 101], Selz et al. Manuscript |
| Lake Malawi cichlids Pseudotropheus fainzilberi and P. emmiltos | Reproductively isolated species with perhaps mild gene flow | Probably not direct sister species | Yes | Different MHC profiles between the populations | Not known | No data | No data | Yes | Divergent MHC profiles between the populations | Not known | Indirect evidence. Olfactory plays a role in mate choice which could mediate effects of divergent MHC profiles | Geographically parapatric | [67, 143, 144] |
| Alpine charr in Norway | Conspecific parapatric populations | No data | Yes, profundal ecotype harbours significantly fewer infections compared to littoral/pelagic ecotype | No data | Not known | No data | No data | Yes | Not known | No tested | Not tested | Parapatric | [59] |
| Benthic and pelagic ecotypes of whitefish in two lakes in northern Norway | Conspecific parapatric populations | No data | Yes, divergence in infections corresponds with the divergence in diet of the ecotypes | No data | Not known | No data | No data | Yes | Not known | Not tested | Not tested | Parapatric | [60] |
| Populations of guppies in Trinidad | Allopatric/parapatric populations from different rivers with no reproductive isolation | No data | Yes, populations were differently infected with Gyrodactylus monogeneans | Different MHC allele frequencies among the populations, individuals carrying certain allele had fewer parasites | Not known | No data | No data | Not known | Yes, different MHC allele frequencies between the populations | Not tested | MHC could act as a homogenizing mechanism counteracting speciation among the populations although mechanisms is not tested | Allopatric/ parapatric | [40] |
| Whitefish in Swiss prealpine lakes | Complete speciation (or speciation reversal) continuum | Yes, from microsatellite and AFLP data | Yes, different parasite taxa | No data | Not known but divergence of parasite assemblage increases with genetic differentiation | No data | No data | Yes, inferred from microsatellite Fst in sympatry | No data | Not known | Not known | Geographically sympatric, ecologically parapatric | [62, 145] |
Bird | Mountain white-crowned sparrows | Conspecific populations | No data, but very likely | No data | No data | Not known | Yes, immigrant individuals had higher infection rates and lower reproductive success | No, hybrids were at a selective advantage | Yes, partially | Not known, but resident males sing a local dialect | It is based on song which might be a revealing signal | Not tested | Parapatric | [71, 75] |
Bird | Collared and pied flycatchers | Distinct sympatric species with a hybrid zone | Probably, recently diverged species | Differences in infection rate between the species | No difference in immune responses between the species | Not known | No data | No, hybrids had intermediate infection levels and immune responses compared to parent populations | Yes | No data | Not tested | Not tested | Single population | [74] |
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