Parthenogenesis and the Evolution of Anisogamy

Recently, it was pointed out that classic models for the evolution of anisogamy do not take into account the possibility of parthenogenetic reproduction, even though sex is facultative in many relevant taxa (e.g., algae) that harbour both anisogamous and isogamous species. Here, we complement this recent analysis with an approach where we assume that the relationship between progeny size and its survival may differ between parthenogenetically and sexually produced progeny, favouring either the former or the latter. We show that previous findings that parthenogenesis can stabilise isogamy relative to the obligate sex case, extend to our scenarios. We additionally investigate two different ways for one mating type to take over the entire population. First, parthenogenesis can lead to biased sex ratios that are sufficiently extreme that one type can displace the other, leading to de facto asexuality for the remaining type that now lacks partners to fuse with. This process involves positive feedback: microgametes, being numerous, lack opportunities for syngamy, and should they proliferate parthenogenetically, the next generation makes this asexual route even more prominent for microgametes. Second, we consider mutations to strict asexuality in producers of micro- or macrogametes, and show that the prospects of asexual invasion depend strongly on the mating type in which the mutation arises. Perhaps most interestingly, we also find scenarios in which parthenogens have an intrinsic survival advantage yet facultatively sexual isogamous populations are robust to the invasion of asexuals, despite us assuming no genetic benefits of recombination. Here, equal contribution from both mating types to zygotes that are sufficiently well provisioned can outweigh the additional costs associated with syngamy.

Parthenogenesis and the Evolution of Anisogamy

Recently, it was pointed out (Lehtonen et al., 2021) that classic models for the evolution of anisogamy do not take into account the possibility of parthenogenetic reproduction, even though sex is facultative in many relevant taxa (e.g. algae) that harbour both anisogamous and isogamous species. Here we complement the analysis of (Lehtonen et al., 2021) with an approach where we assume that the relationship between progeny size and its survival may differ between parthenogenetically and sexually produced progeny, favouring either the former or the latter. We show that the findings of (Lehtonen et al., 2021), that parthenogenesis can stabilise isogamy relative to the obligate sex case, extend to our scenarios. We additionally investigate two different ways for one mating type to take over the entire population. First, parthenogenesis can lead to biased sex ratios that are sufficiently extreme that one type can displace the other, leading to de facto asexuality for the remaining type that now lacks partners to fuse with. This process involves positive feedback: microgametes, being numerous, lack opportunities for syngamy, and should they proliferate parthenogenetically, the next generation makes this asexual route even more prominent for microgametes. Second, we consider mutations to strict asexuality in producers of micro- or macrogametes, and show that the prospects of asexual invasion depend strongly on the mating type in which the mutation arises. Perhaps most interestingly, we also find scenarios in which parthenogens have an intrinsic survival advantage yet facultatively sexual isogamous populations are robust to the invasion of asexuals, despite us assuming no genetic benefits of recombination. Here equal contribution from both mating types to zygotes that are sufficiently well provisioned to outweigh the additional costs associated with syngamy.

Chlorantraniliprole impact on survival and progeny quality of the pupa of the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

The insecticide chlorantraniliprole is recommended for integrated pest management programmes of caterpillar (Lepidoptera) pest species. This insecticide is considered harmless to parasitoids, but its selectivity may vary with the species of natural enemy, few of which were subjected to testing. Furthermore, in addition to the active ingredient, formulation adjuvants may improve insecticide efficiency, but also its impact on nontargeted organisms. Here the chlorantraniliprole effect and its interaction with adjuvant on the survival and qualitative parameters of progeny of the nontarget parasitoid Palmistichus elaeisis (Delvare and LaSalle) (Hymenoptera: Eulophidae) were studied. The treatments used were: chrolantraniliprole (T1), chlorantraniliprole+surfactant (T2), and deionised water (T3, control). Pupae of Diaphania hyalinata Linnaeus (Lepidoptera: Crambidae) were subjected to these treatments for 24 hours and offered to the adult parasitoids. Chlorantraniliprole and chlorantraniliprole+surfactant did not elicit direct toxicity to female parasitoids. However, chlorantraniliprole and its combination with surfactant reduced the head capsule width of the female progeny. This insecticide alone also reduced emergence and the progeny metatibia length. Chlorantraniliprole did not induce mortality of P. elaeisis adults, but its negative impact on the emergence and progeny size of this parasitoid suggests an important sublethal effect to be considered.

Demographic structure and genetic diversity of the endangered Bísaro pig: Evolution and current status

Bísaro pig, a local endangered swine breed, has gained popularity in the recent years. A complete pedigree was used to evaluate the population structure and investigate the current breed’s genetic variability in two reference populations (AlivePop and AliveBpop). Since the breed’s foundation, the number of registered animals, producers, and farrowing records has increased. The mean progeny size for sires was 116.17 ± 210.81, and 3.24% of the breeding boars originated 26.54% of all registered births showing a marked unbalanced use of certain sires. The mean calculated equivalent generations was 4.54, and 98.1% of all the animals had known parents, indicating a good degree of pedigree completion and depth. Approximately half of the individuals were inbred, with average inbreeding values of 10.41, 9.02, and 8.58% for the whole and reference populations, respectively. Considering both reference populations, a low effective founder/ancestor ratio was obtained (1.12), showing a well-balanced founder/ancestor contribution, and subsequent genetic transfer. However, the effective founder/founder ratio was particularly low (0.06 and 0.12) compared with other native breeds. The founder genome/effective founder ratios were 0.37 and 0.41 for AlivePop and AliveBpop. Contrarily to the whole population, the random genetic drift weighted significantly more than the drift due to unequal founder contribution in the reference populations. The effective population size based on the increase in coancestry ranged from 62.39 and 54.66, and 16.74 and 24.84 based on the increase of individual inbreeding, for the whole and reference populations. The genetic conservation index steadily grew over the years with a mean value of 6.53 for the whole pedigree. Genetic variability losses and diffuse structuring might have occurred in the Bísaro population. Notwithstanding, the recent genetic variability indicators seem positive, yet supported by an open herdbook policy. These characteristics must be taken into account to define future mating policies and selection programs.

Genetic analysis using parent-progeny relationship for wood quality traits in Norway spruce (Picea abies (L.) Karst.)

Two-generations pedigree involving 524 plus trees and their open-pollinated (OP) progenies were jointly studied to estimate parent-progeny correlation and heritability. Three wood traits (wood density, MFA, and MOE) were determined by SilviS-can in one ramet per plus tree and 12 OP progenies. Three ramets per plus tree and 12 OP were also measured with two indirect methods, Pilodyn and Hitman. The overall correlation between OP-based breeding values and plus tree-based phenotypes was low to moderate for all traits. The correlations between the phenotypic values of the mother trees and the breeding values estimated on their half-sib pro-genies are low to moderate. Reasons for this may be experimental errors in progeny trials and lack of experimental design in archives, contributing to the parent and progeny correlation. The management practices in the archive may contribute more to such low correlation. Offspring progeny heritability estimates based on SilviScan measurements were higher than parent-offspring regression using one single ramet from the archive. Moreover, when three ramets were measured the parent-offspring regression heritability estimates were higher than those based solely on progeny data for the Pilodyn and Hitman on the standing trees. The standard error of the heritability estimates decreased with increasing progeny size.

Inheritance of mature leaf properties in grapevine progeny obtained by crossing Muscat Hamburg and Villard Blanc cultivars

and inheritance mode of six properties of the mature leaf (size of blade, number of lobes, shape of teeth, general shape of petiole sinus, density of prostrate and erect hairs between veins on the lower side of blade) were analyzed in 90 seedlings of the F1 generation from the crossing combination of Muscat Hamburg x Villard Blanc. The properties analyzed were classified according to the OIV system of classification and ?2 test was used to determine the inheritance mode. A substantial variability of the analyzed characteristics was recorded in the hybrid progeny. Size of blade, number of lobes, shape of teeth and general shape of petiole sinus were most probably affected by a great number of genetic factors. Monogenic inheritance was determined with regard to the density of prostrate and erect hairs between veins on the lower side of blade.