Table 1.
Overview of all taxonomic groups with PGE
| Class | Order | Clade | Number of species | Type of PGE | Male soma | Sex chromosomes | Ancestral SD | Sib-mating/Inbreeding* | References |
|---|---|---|---|---|---|---|---|---|---|
| Acari | Mesostigmata | Phytoseiidae, Otopheidomenidae, Ascoidea | 2000 (10) | Embryonic PGE | Haploid (genome loss) | No sex chr. | XX/XY or XX/X0 | Strong evidence (WM, WF, SB, SM, PS) | (Nelson-Rees et al. 1980; Norton et al. 1993; Nagelkerke & Sabelis 1998; Burt & Trivers 2006) |
| Collembola | Symphypleona | Symphypleona | 1180 (6) | Germline PGE | Diploid with X elimination | X1X2X1X2/X1X200 | XX/X0 | Some evidence (WM, WF, PG, SB) | (Dallai et al. 2001; Burt & Trivers 2006) |
| Insecta | Coleoptera | Cryphalini | 190 (1) | Germline PGE | Diploid with paternal genome silencing | No sex chr. | XX/XY | Strong evidence (WM, SB, SM, PG) | (Brun et al. 1995; Borsa & Kjellberg 1996; Gauthier 2010) |
| Insecta | Diptera | Cecidomyiidae | 6168 (22) | Germline PGE | Diploid with X elimination | XX/X0 | XX/XY | No evidence | (Painter 1966; Stuart & Hatchett 1991; Burt & Trivers 2006; Benatti et al. 2010) |
| Insecta | Diptera | Sciaridae | 2300 (10) | Germline PGE | Diploid with X elimination | XX/X0 | XX/XY | No evidence | (Metz 1938; Crouse 1960; Haig 1993a, b; Goday & Esteban 2001; Sánchez 2010) |
| Insecta | Hemiptera | Neococcoidea | 4000 (270) | Germline PGE | Diploid with paternal genome silencing | No sex chr. | XX/X0 | Some evidence (WF, PS, PG) | (Brown & Nur 1964; Nur 1990; Gavrilov 2007; Ross et al. 2010a; Martins et al. 2012) |
| Insecta$ | Hemiptera | Diaspididae | 2650 (139) | Embryonic PGE | Haploid (genome loss) | No sex chr. | XX/X0 | Some evidence (WF, PS) | (Brown & Nur 1964; Nur 1990) |
| Insecta | Phthiraptera | Pediculus humanus humanus | ? (1) | Germline PGE | Unknown | No sex chr. | XX/XY? | Some evidence (PS, PG, SB, WM, WF) | (Perotti et al. 2004; McMeniman & Barker 2005; Ascunce et al. 2013) |
Rows represent independent origins of PGE, except for Diaspididae (indicated by$), which represents change in type of PGE (germline → embryonic). Number of species column: estimate assumes PGE is conserved across whole clade; number of species for which there is direct evidence of PGE given in parentheses. Types of PGE: ‘embryonic’ when complete paternal genome is eliminated from both soma and germline in early embryogenesis; ‘germline’ when paternal genome only completely eliminated in the germline during spermatogenesis. Male soma and sex-chromosome information based on karyotype analysis of species with PGE. Ancestral-SD system inferred from karyotype data for diploid sister groups. Inbreeding inferred from FIS, mating system and sex-ratio data (WM, wingless males; WF, wingless females; SB, female-biased sex ratios; PG, population-genetic evidence of low genetic diversity and excess homozygosity; PS, life history leading to strong meta-population structure; SM, frequent sib-mating).