Does paternity or paternal investment determine the level of paternal care and does female choice explain egg stealing in the fifteen-spined stickleback?

An earlier field study on the fifteen-spined stickleback (Spinachia spinachia) showed that frequent male—male interactionsresult in high frequencies of sneaking and egg stealing. Moreover,sneaking behavior was performed not only by males adoptingalternative mating strategies, but also by males with theirown nests. The advantage of sneaking is easily understood, but it is more difficult to explain the evolutionary benefitof stealing eggs from other males. I investigated whether malessuffering from sneaking adjust their paternal effort in relationto their degree of paternity. I also examined whether femalesprefer males that have more eggs in their nests, as this couldexplain egg stealing. There was no relationship between thedegree of paternity and fanning activity, hatching success,or nest defense. However, the older the eggs become, the morethe males increase their attack rate toward potential egg predators(goldsinny wrasse and shore crabs). Thus, males adjusted theirlevel of defense to the amount of energy and time already investedin the clutch. Females did not prefer males with more eggs intheir nests. On the contrary, females preferred males withreduced clutches over males with enlarged clutches. Therefore,female choice is unlikely to be a driving force behind eggstealing in this species.     

THE INFLUENCE OF THE MATING SYSTEM ON SEED SIZE VARIATION IN CRINUM ERUBESCENS (AMARYLLIDACEAE)

We present evidence that extreme seed size variation in fruits of Crinum erubescens (range: 0.1 to 66.5 g per seed) occurs when mating pairs are inbred, either from selfing or biparental inbreeding. Several relatively uniform seeds of intermediate size are produced when pollen from several pollen donors is applied simultaneously to a flower. Selfed fruits and some fruits pollinated with a single pollen donor produce both large and small seeds, although selfed fruits produce fewer seeds than outcrossed fruit. These results are contrary to the hypothesis that variation in seed size is attributable to either pollen competition or differential allocation of maternal resource to seeds of different genotypes.     

DNA “fingerprints” and paternity ascertainment in chimpanzees (Pan troglodytes)

Highly variable regions of DNA are found in a wide diversity of organisms and are typically composed of alleles consisting of a variable number of tandem repeats (VNTRs) of a short core sequence. DNA fingerprinting probes are VNTR probes that simultaneously detect a large number of similar VNTRs in the target DNA. The highly polymorphic pattern observed in a DNA fingerprint allows resolution of questions concerning individual identification. M13 phage was used to fingerprint captive chimpanzees for paternity ascertainment. Although the probability of band sharing among captive chimps appears to be higher than among some other reported captive and feral animal populations, the probe is highly useful and can be expected to become more widely used in the genetic management of captive populations.     

Probability of paternity exclusion and the number of loci needed to determine the fathers in a troop of macaques

We calculated the probability of paternity exclusion (P) in 6 troops of rhesus and Japanese macaques housed in open enclosures and 68 wild troops of Japanese, crab-eating, and toque macaques using 33 genetic loci which encoded the blood protein variations detected by electrophoretic techniques. In the open enclosures, especially of rhesus troops, we obtained a fairly high probability of paternity exclusion and succeeded in determining the fathers of offspring. However, we found significant differences between the observed and calculated probabilities in most of the troops. These differences were ascribed to a situation whereby the Hardy-Weinberg equilibrium had not been attained in the troops and/or the numbers of variable loci were too small. In the wild troops of Japanese, crab-eating, and toque macaques, the means ofP were 0.2274 (0.0192–0.5017), 0.4635 (0.1676–0.7151), and 0.7382 (0.6266–0.7954), respectively. We also estimated the number of loci needed to determine the fathers of offspring with a probability of 0.8 assuming that ten males were present in the troop. The estimated number was about 13.5 times, 5 times and 1.8 times the number of loci examined on average in the troops of Japanese, crab-eating and toque macaques, respectively. This means that determination of most of the fathers of offspring in wild troops of these macaques, even of toque macaques which have a rather high probability of paternity exclusion, is difficult so long as we employ only electrophoretic techniques.     

Numbers of sporophytic self-incompatibility alleles in populations of wild radish

Summary To estimate the numbers of sporophytic S-alleles in two adjacent populations of wild radish, we performed 701 reciprocal crosses among 50 individuals. Each cross was replicated five times in each direction. Sixteen plants were fully intercompatible, indicating the presence of at least 32 S-alleles in the two populations. A minimum of 22 S-alleles occur in a single population. The frequency of incompatibility was significantly higher for within-population crosses (14.5%) than for between-population crosses (7.8%). This suggests that the two populations differ in the composition and frequency of alleles at the S-locus.     

POLLEN-TUBE COMPETITION AND MALE FITNESS IN HIBISCUS MOSCHEUTOS

The stigmas of animal-pollinated flowers often capture more pollen than is needed to fertilize all available ovules, and mixed-donor pollen loads are probably common. When this is the case, variation in average pollen-tube growth rates can potentially affect the number of seeds sired by a given plant. Despite considerable interest in effects of postpollination processes on male fitness, little is known about the extent of variation in pollen performance among plants from natural populations. To examine this question in Hibiscus moscheutos (rose mallow), we conducted mixed-donor hand-pollination experiments with 39 pollen donors bearing distinctive isozyme markers. Pairs of competing donors were compared on sets of 11 to 15 recipient plants per pair. These donors often differed in the proportions of seeds they sired, with the maximum deviation from an expected ratio of 50:50 being 68:32. Furthermore, three intensively studied plants exhibited consistent trends in relative pollen performance when each was tested against (1) the same three competitors, and (2) groups of 14 competitors chosen at random from the study population. In a separate experiment, we investigated the effects of salinity stress and high soil nutrients on pollen performance. These environmental factors had anticipated effects on leaf production, flower production, and petal length, but style length and (most importantly) the number of seeds sired relative to a standard pollen donor were not affected. In summary, this study provides the strongest evidence to date that pollen-tube competitive ability varies among coexisting plants and may be an important component of male fitness in plants.     

RELATIVE SUCCESS OF SELF AND OUTCROSS POLLEN COMPARING MIXED- AND SINGLE-DONOR POLLINATIONS IN AQUILEGIA CAERULEA

Flowers frequently receive both self (S) and outcross (OC) pollen, but S pollen often sires proportionally fewer seeds. Failure of S pollen can reflect evolved mechanisms that promote outcrossing and/or inbreeding depression expressed during seed development. The relative importance of these two processes was investigated in Aquilegia caerulea, a self-compatible perennial herb. In the field I performed single-donor (S or OC) and mixed-donor (S plus OC) pollinations to compare the relative success of both pollen types at various stages from pollen germination to seed maturity. Single-donor S pollinations produced significantly fewer and lighter seeds (x decrease = 12% and 3%, respectively) than OC pollinations. Abortion rates differed by an average of 38% whereas fertilization rates differed by only 5%, indicating that most differences in seed number arose postzygotically. This suggests that inbreeding depression was responsible for most failure of S pollen. One prezygotic effect measured was that 10% fewer S than OC pollen tubes reached ovaries after 42 hr, suggesting S pollen might fertilize proportionately fewer ovules after mixed pollination. Using allozyme markers, I found mixed-donor pollinations produced significantly more and heavier outcrossed than selfed seeds. However, the proportion of selfed seed, fertilized ovules, and aborted seeds for mixed-donor fruits were each predictable from pollen performance in single-donor fruits, suggesting that differential paternity is best explained by inbreeding depression during seed development. Even given these similarities between mixed- and single-donor fruits in the relative performance of S and OC pollen, both individual seed weight and seed set were significantly higher in multiply-sired fruits.     

Paternity assessment and population subdivision in a natural population of the larger mouse-eared bat Myotis myotis

A hypervariable simple sequence locus and mitochondrial D-loop sequences were used to analyse genetically a natural population of the larger mouse-eared bat Myotis myotis in southern Bavaria. Tests for population subdivision and direct observations suggest that females return to their natal sites, while males disperse. The males present in female nursery colonies are not related to the females. Paternity assessment for 46 offspring from a particular nursery colony showed that there are no males that monopolize the reproduction, and that the resident males in the colony had only a small mating success. Instead, the results suggest that females actively seek matings outside their colony. Most interestingly, it appears that a group of males about 16 km away from the nursery colony had a relatively high mating success and that this group of males may be related to the females of the nursery colonies. If this finding can be confirmed in a larger study, it may have important consequences for future conservation strategies.     

Resolving genetic relationships with microsatellite markers: a parentage testing system for the swallow Hirundo rustica

Eight polymorphic microsatellite markers from the swallow were isolated and characterized. Extraordinary variability was revealed at the HrU6 locus with 45 different alleles scored among 46 unrelated individuals. The probability that the same genotype combination would occur in two random and unrelated individuals at six selected loci was as low as 1.3 × 10^-8 and the combined exclusion probability was 0.9996. Stable Mendelian inheritance was observed in about 1000 meioses. No significant linkage was revealed and for almost all combinations of marker-pairs, linkage closer than 5 cM could be excluded. At two loci, null (nonamplifying) alleles were encountered. Thirteen (30%) extra-pair offspring were identified in 5 (56%) broods when applying the marker set on a nearly complete swallow colony. We were able to identify a single male from the other families in the colony as the most likely father for nine of the 13 extra-pair offspring.     

Multiple paternity in the red-eyed treefrog Agalychnis callidryas (Cope)

DNA fingerprinting of tadpoles from two different ‘one female-two male’ matings of the red-eyed treefrog, Agalychnis callidryas, revealed multiple paternity of offspring. Offspring were assigned paternity based on bands shared with the putative father, but not shared between putative fathers or with the mother. Paternity was split 44/56% and 36/64% in two matings. These results do not support a hypothesis of sperm priority in access to unfertilized eggs by primary males. Multiple paternity may be commonplace in species of anurans with matings by multiple males.