. Biology of the Heteromyidae. Heteromyidae. 464 WHITAKER ET perognathi texanus brevispinosus inaequalis formosus deserti dipodomius utahensis microdipodops postscutatus Fig. 4. Phenogram showing Geomylicus re- lationship using 23 female and 22 male charac- ters, coded into discrete categories. provided our initial assumption that one Eimeria evolved per host. However, it might not be that simple. The "island hopping" process might be in effect, yet one Eimeria could move from one host to another, un- dergo speciation there, then later move back to the first and again undergo sp
. Biology of the Heteromyidae. Heteromyidae. 464 WHITAKER ET perognathi texanus brevispinosus inaequalis formosus deserti dipodomius utahensis microdipodops postscutatus Fig. 4. Phenogram showing Geomylicus re- lationship using 23 female and 22 male charac- ters, coded into discrete categories. provided our initial assumption that one Eimeria evolved per host. However, it might not be that simple. The "island hopping" process might be in effect, yet one Eimeria could move from one host to another, un- dergo speciation there, then later move back to the first and again undergo speciation, creating three species in two hosts. Much more information on relationships of both hosts and parasites is needed before we can go very far in this direction. However, we have produced a phenogram using the het- eromyid species used by Geomylichus (Fig. 4). It did not fit the heteromyid evolutionary tree very well. This may be because the spe- cies of Geomylichus moved between host species and even genera where the hosts were sympatric, then underwent speciation there, with the differential hosts acting as primary isolating mechanisms. The situation is simpler in Liomys if we assume one species per host. Eimeria picta must have evolved in L. pictus, and E. lio- mysis in L. irroratus, but then the latter par- asite invaded L. pictus after speciation had been completed. In Chaetodipus, more in- formation is needed before much can be said. There are of course additional possi- bilities, especially involving reinvasion. Ex- amination of additional hosts will undoubt- edly throw additional light on the situation. We suspect that this is at least the general way in which evolution proceeded in this group. Many authors have tended to think of parasites as overspecialized evolutionary dead ends. We agree with Price (1980) who expressed a different view in the introduc- tion to his book. Evolutionary Biology of Parasites. He argued that "no group of or- ganisms on this ea
Size: 1649px × 1516px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, bookcontributorharv
