Figures

- Sex, bugs and Haldane's rule: the nematode genus Pristionchus in the United States

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Figure 1   Map of the Eastern US showing the distribution of sampled Pristionchus species. Material has been obtained from the following sampling sites: Massachusetts (Two locations: Carver and Centerville), New York (six locations: Bellona, Waterloo, Hoover farm, golf court I and II, Geneva), Ohio (One location : Wooster), Iowa (One location: near Bellevue, Nebraska), Kansas (One location: Greensburg), Texas (One location: Austin), and Nebraska (five locations: Lincoln: pioneer park, wilderness park, nine mile prairie; Bennett, Nemaha).

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Figure 2  Alignment of SSU sequences. Sequences of 13 Pristionchus and one Koerneria species were aligned manually. Dashes (-) indicate identity to the majority consensus sequence at the top; asterisks (*) indicate alignment gaps. Numbering refers to the SSU segment obtained in this study. The sequences have been submitted to the GenBank database and are available under the accession codes DQ270018-DQ270025 and DQ419900-DQ419904. 

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Figure 3  Pie charts indicating the ratio of gonochoristic (white) to hermaphroditic (grey) Pristionchus isolates in the Eastern US and Western Europe.  

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Figure 4  Phylogenic maximum likelihood tree based on SSU sequences of the genus Pristionchus. As outgroup the sequence of Koerneria sp. was included as the closest related genus to Pristionchus. A single best tree was obtained using the Kimura 2-parameter model (Kimura 1980) with Ts/Tv = 1,4727, equal base frequencies, and a γ-correction with shape parameter α = 0,2381. Numbers at nodes indicate bootstrap values after 1000 replications. E, species observed in Western Europe; A, species observed in North-America (this study).  

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Figure 5  Alignment of the coding sequences of the ribosomal protein genes rpl-26, rpl-28, and rps-14 of P. maupasi, P. aerivorus, P. pseudaerivorus, P. americanus, and P. marianneae. Dashes (-) indicate identity to the majority consensus sequence at the top. 

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Figure 6 F1 hybrids of P. aerivorus and P. pseudaerivorus n. sp. follow Haldane's rule. (A) Results of crosses between four strains of P. aerivorus (P. aer) from New York (NY), Ohio (OH), Texas (TX) and Nebraska (NE) and three strains of P. pseudaerivorus n. sp. (P. pseu) from Texas (TX), Indian Cave, Nebraska (NE) and Lincoln, Nebraska (LNE). Each strain was crossed with all other strains in a reciprocal manner. Columns represent female animals and rows represent males used for crosses. Mating was performed in triplicate, placing one virgin female and one male on a plate. Numbers show the total of eggs laid by one female. In brackets, the number of eggs that developed into phenotypic female vs. male progeny is indicated. The difference between the upper number and the sum of the numbers in brackets is accounted for by unfertilized eggs and embryonic lethality commonly observed after crosses within and between animals of these two species. The given numbers represent the result of the experiment with the highest number of offspring. (B) SSU sequence profile of P. aerivorus, P. pseudaerivorus n. sp. and a hybrid between the two species.