Mixed-Mating Model of Reproduction Revealed in European Phytophthora cactorum by ddRADseq and Effector Gene Sequence Data

A population study of Phytophthora cactorum was performed using ddRADseq sequence variation analysis completed by the analysis of effector genes—RXLR6, RXLR7 and SCR113. The population structure was described by F-statistics, heterozygosity, nucleotide diversity, number of private alleles, number of polymorphic sites, kinship coefficient and structure analysis. The population of P. cactorum in Europe seems to be structured into host-associated groups. The isolates from woody hosts are structured into four groups described previously, while isolates from strawberry form another group. The groups are diverse in effector gene composition and the frequency of outbreeding. When populations from strawberry were analysed, both asexual reproduction and occasional outbreeding confirmed by gene flow among distinct populations were detected. Therefore, distinct P. cactorum populations differ in the level of heterozygosity. The data support the theory of the mixed-mating model for P. cactorum, comprising frequent asexual behaviour and inbreeding alternating with occasional outbreeding. Because P. cactorum is not indigenous to Europe, such variability is probably caused by multiple introductions of different lineages from the area of its original distribution, and the different histories of sexual recombination and host adaptation of particular populations.

Variations in reproductive and egg traits correlation estimates of two strains of Archachatina marginata snails (var. ovum and var. saturalis) and crosses

A study was conducted to ariations in the reproductive traits and egg traitscorrelation estimates of the two strains of Archachatina marginata snails (var. ovum and var. saturalis) and their crosses. Ninety sexually mature A. marginata snails, forty-five each of the two strains (var. saturalis and var. ovum) were selected from a base population for the study. he live weight of the snails ranged from 256.43 – 566.25 g for both strains. Selection of the snails was based on active appearance and lack of injury on the foot and on shells. The snails were randomly allotted into three mating models (treatments) of 30 each of var. saturalis, var. ovum and mixed strains (at 15 var. ovum : 15 var. saturalis). The models were designated as homozygous var. ovum main cross (AMO X AMO), homozygous var. saturalis main cross (AMS X AMS) and heterozygous (var. ovum x var. saturalis) cross (AMO X AMS). Each of the three models was replicated 15 times with two snails to a tub/cell for purposes of reproduction. Results from the study showed that the three mating models expressed significant (P<0.05) differences in the reproductive traits evaluated. Whereas some of the traits were not significantly (P>0.05) different between the AMO X AMO and AMO X AMS mating models, significant (P<0.05) differences existed between all the traits when the AMS AMS mating model was compared with the AMO X AMO and AMO X AMS mating models. The clutch size ranged from 7.00±0.35 (AMS X AMS) through 9.40±0.35 (AMO X AMS) to 9.90±0.35 (AMO X AMO), while the values for mean egg weight at lay ranged from 1.59±0.03 g (AMS X AMS) through 1.78±0.03 g (AMO X AMO) to 1.79±0.03 g (AMO X AMS). Percent hatchability value was highest in the AMO X AMO mating model (93.30 %), followed by the AMS X AMS mating model (91.10 %), while the AMO X AMS mating model recorded the lowest value (88.50 %). Percent survivability value was highest in the AMO X AMS mating model (84.00 %), followed by the AMO X AMO mating model (82.00 %), while the AMS X AMS mating model recorded the lowest value (80.00 %). The egg traits correlation estimates (rp) revealed that except for one pair of trait each in the mating models, all the other pairs of traits expressed positive and significant correlation coefficients/values. The AMO X AMS mating model recorded the highest correlation (rp) value (0.826) for the pair of ELH vs EWH, while the AMS X AMS mating model recorded the lowest correlation (rp) value (– 0.058) for the pair of ELH vs CSE. The percent egg shell colour distribution showed that the shell of eggs laid by the homozygous crosses (AMO X AMO and AMS X AMS) expressed two colours. The egg shell of eggs laid by AMO X AMO mating model expressed mikado yellowand maize yellow colours, while those laid by AMS X AMS mating model expressed Mikado yellow and amber colours. The shell of eggs laid by the heterozygous cross however expressed three colours; mikado yellow, maize yellow and amber. Based on the reproductive traits results, it could be recommended that the AMO X AMS mating model be adopted by farmers for optimum production and returns on investment.

Microsatellite analysis of the mating system of Bruguiera gymnorrhiza and Kandelia obovata

Microsatellite loci were used for estimating mating system for three populations of B. gymnorrhiza and K. obovata (Rhizophoracea) in Okinawa, Japan. Mother trees and thirty offspring of individual samples representing the population of both species were genotyped at five microsatellites. The mating system was examined using two approaches: a mixed mating model of multilocus testing, implemented by MLTR program and outcrossing rate from the level of inbreeding. Mating system analysis showed multilocus outcrossing rates (tm) for both species was 0.850-1.000 and 0.780-0.938 respectively. By contrast, according to inbreeding level, tm was lower than MLRT: 0.495-1.028 and 0.480-0.612 of both species respectively. However, biparental inbreeding (tm- ts) was diverse from zero both species for all three populations, showing that cross-fertilization events may ensue between the relatives both species. This data as well means the genetic relatedness (r) for B. gymnorrhiza and K. obovata were 0.108±0.025 and 0.032±0.09 respectively. Average relatedness was below 0.25, the value for a half-sib relationship. These results suggest that postulation of a half-sib relationship among progeny of open-pollinated families is opposed for both mangrove tree species.

Fluid limit for the Poisson encounter-mating model

Stochastic encounter-mating (SEM) models describe monogamous permanent pair formation in finite zoological populations of multitype females and males. In this paper we study SEM models with Poisson firing times. First, we prove that the model enjoys a fluid limit as the population size diverges, that is, the stochastic dynamics converges to a deterministic system governed by coupled ordinary differential equations (ODEs). Then we convert these ODEs to the well-known Lotka–Volterra and replicator equations from population dynamics. Next, under the so-called fine balance condition which characterizes panmixia, we solve the corresponding replicator equations and give an exact expression for the fluid limit. Finally, we consider the case with two types of female and male. Without the fine balance assumption, but under certain symmetry conditions, we give an explicit formula for the limiting mating pattern, and then use it to characterize assortative mating.

Aphrodisiac property of aerial parts of Trianthema decandra Linn.

Aim of the study is to identify and evaluate the active constituents present in the aerial parts of Trianthema decandra Linn. The fresh aerial parts of plant were collected, dried under shade, coarsely powdered and successively extracted with different solvents based on increasing order of polarity. All the extracts of the plant were subjected for phytochemical screening. The methanol extract was screened for aphrodisiac activity. The sexual activity of male mice in Assessment of mating model was determined by administering methanolic extract of Trianthema decandra of different doses and each male mouse was placed in separate cage. After one hour, five oestrous females were placed into each cage and cohabitated overnight. The vaginal smear of each female mouse was examined next day under the microscope to confirm mating by the presence of sperms. To study the Effect on fertility in mice model, different groups of animals (mice) were treated as above and each male mouse was placed in separate cage. After one hour, one oestrous female with proven fertility was admitted into each cage and cohabitated overnight. These females were watched for pregnancy and birth of offspring’s. In the conclusion, out of all test extract doses of Trianthema decandra, medium and high dose showed significant aphrodisiac activity when compared with control and standard groups. Hence this reveals that Trianthema decandra have fertility enhancing activity. Further research is needed to identify biologically active constituents for fertility enhancing activity.

Assortative mating without assortative preference

Assortative mating—marriage of a man and a woman with similar social characteristics—is a commonly observed phenomenon. In the existing literature in both sociology and economics, this phenomenon has mainly been attributed to individuals’ conscious preferences for assortative mating. In this paper, we show that patterns of assortative mating may arise from another structural source even if individuals do not have assortative preferences or possess complementary attributes: dynamic processes of marriages in a closed system. For a given cohort of youth in a finite population, as the percentage of married persons increases, unmarried persons who newly enter marriage are systematically different from those who married earlier, giving rise to the phenomenon of assortative mating. We use microsimulation methods to illustrate this dynamic process, using first the conventional deterministic Gale–Shapley model, then a probabilistic Gale–Shapley model, and then two versions of the encounter mating model.