Higher investment in flight morphology does not trade off with fecundity estimates in a poleward range‐expanding damselfly

1. Evolutionary increases in dispersal‐related traits are frequently documented during range expansions. Investment in flight‐related traits is energetically costly and a trade‐off with fecundity may be expected during range expansion. 2. However, in contrast to wing‐dimorphic species, this trade‐off is not general in wing‐monomorphic species. In the absence of a dispersal‐‐fecundity trade‐off, an increased investment in clutch size at the expansion front is expected possibly at a cost of reduced offspring size. 3. The study evaluated investment in female flight morphology and fecundity‐related traits (clutch size, hatchling size) and potential trade‐offs among these traits in replicated populations of the poleward range‐expanding damselfly Coenagrion scitulum. 4. Females at the expansion front had a higher relative thorax length, indicating an increased investment in flight; this can be explained by spatial sorting of dispersal ability or in situ natural selection at the expansion front. Edge females produced larger hatchlings, however, this pattern was totally driven by the population‐specific thermal larval regimes and could not be attributed to the range expansion per se. By contrast, clutch sizes did not differ between core and edge populations. There was no signal of a dispersal–fecundity trade‐off either for a trade‐off between clutch size and hatchling size. 5. These results indicate that evolution of a higher dispersal ability at the expansion front of C. scitulum does not trade off with investment in fecundity, hence a dispersal–fecundity trade‐off is unlikely to slow down range expansion of this species.     

A synthesis of genetic connectivity in deep‐sea fauna and implications for marine reserve design

With anthropogenic impacts rapidly advancing into deeper waters, there is growing interest in establishing deep‐sea marine protected areas (MPAs) or reserves. Reserve design depends on estimates of connectivity and scales of dispersal for the taxa of interest. Deep‐sea taxa are hypothesized to disperse greater distances than shallow‐water taxa, which implies that reserves would need to be larger in size and networks could be more widely spaced; however, this paradigm has not been tested. We compiled population genetic studies of deep‐sea fauna and estimated dispersal distances for 51 studies using a method based on isolation‐by‐distance slopes. Estimates of dispersal distance ranged from 0.24 km to 2028 km with a geometric mean of 33.2 km and differed in relation to taxonomic and life‐history factors as well as several study parameters. Dispersal distances were generally greater for fishes than invertebrates with the Mollusca being the least dispersive sampled phylum. Species that are pelagic as adults were more dispersive than those with sessile or sedentary lifestyles. Benthic species from soft‐substrate habitats were generally less dispersive than species from hard substrate, demersal or pelagic habitats. As expected, species with pelagic and/or feeding (planktotrophic) larvae were more dispersive than other larval types. Many of these comparisons were confounded by taxonomic or other life‐history differences (e.g. fishes being more dispersive than invertebrates) making any simple interpretation difficult. Our results provide the first rough estimate of the range of dispersal distances in the deep sea and allow comparisons to shallow‐water assemblages. Overall, dispersal distances were greater for deeper taxa, although the differences were not large (0.3–0.6 orders of magnitude between means), and imbalanced sampling of shallow and deep taxa complicates any simple interpretation. Our analyses suggest the scales of dispersal and connectivity for reserve design in the deep sea might be comparable to or slightly larger than those in shallow water. Deep‐sea reserve design will need to consider the enormous variety of taxa, life histories, hydrodynamics, spatial configuration of habitats and patterns of species distributions. The many caveats of our analyses provide a strong impetus for substantial future efforts to assess connectivity of deep‐sea species from a variety of habitats, taxonomic groups and depth zones.     

Does the relationship between offspring size and performance change across the life‐history?

What selection pressures drive the evolution of offspring size? Answering this fundamental question for any species requires an understanding of the relationship between offspring size and offspring fitness. A major goal of evolutionary ecologists has been to estimate this critical relationship, but for organisms with complex lifecycles, logistical constraints restrict most studies to early life‐history stages only. Here, we examine the relationship between offspring size and offspring performance in the field across multiple life‐history stages and across generations in a marine invertebrate .We then use these data to parameterise a simple optimality model to generate predictions of optimal offspring size and determined whether these predictions depended on which estimate of offspring performance was used. We found that offspring size had consistently positive effects on performance (estimated as post‐metamorphic growth, fecundity and reproductive output). We also found that manipulating the experience of offspring during the larval phase changed the way in which offspring size affects performance: offspring size affected post‐metamorphic growth when larvae were allowed to settle immediately but offspring size affected survival when larvae were forced to swim prior to settlement. Despite finding consistently positive effects of offspring size, early measures of the effect of offspring size resulted in the systematic underestimation of optimal offspring size. Surprisingly, the amount of variation in offspring performance that offspring size explained decreased with increasing time in the field but the steepness of the relationship between offspring size and performance actually increased. Our results suggest caution should be exercised when empirically examining offspring size effects – it may not be appropriate to assume that early measures are a good reflection of the actual relationship between offspring size and fitness.     

Nonsignificant isolation by distance implies limited dispersal

Understanding the scale of dispersal is an important consideration in the conservation and management of many species. However, in species in which the high‐dispersal stage is characterized by tiny gametes or offspring, it may be difficult to estimate dispersal directly. This is the case for many marine species, whose pelagic larvae are dispersed by ocean currents by several days or weeks before beginning a benthic, more sedentary, adult stage. As consequence of the high‐dispersal larval stage, many marine species have low genetic structure on large spatial scales (Waples 1998 ; Hellberg 2007 ). Despite the high capacity for dispersal, some tagging studies have found that a surprising number of larvae recruit into the population they were released from (self‐recruitment). However, estimates of self‐recruitment are not informative about mean dispersal between subpopulations. To what extent are limited dispersal estimates from tagging studies compatible with high potential for dispersal and low genetic structure? In this issue, a study on five species of coral reef fish used isolation by distance (IBD) between individuals to estimate mean dispersal distances (Puebla et al. 2012 ). They found that mean dispersal was unexpectedly small (<50 km), given relatively low IBD slopes and long pelagic durations. This study demonstrates how low genetic structure is compatible with limited dispersal in marine species. A comprehensive understanding of dispersal in marine species will involve integrating methods that estimate dispersal over different spatial and temporal scales. Genomic data may increase power to resolve these issues but must be applied carefully to this question.     

Larval growth history determines juvenile growth and survival in a tropical marine fish

Processes that occur around the transition between larval and juvenile life‐stages can have a major effect on the population dynamics of organisms with complex life cycles. We explore the roles of larval history and selective post‐settlement mortality in determining the growth and survival of newly settled individuals of the damselfish, Pomacentrus amboinensis (Pomacentridae). Specifically, we determine whether the direction and intensity of selection on the recruits differs among various size‐classes of predators. A mark‐recapture study showed that individuals who survived 9 or more days were significantly larger at settlement than those that died within the first day (12.3 vs 11.9 mm SL), when mortality was highest (25% d^?1). Censuses revealed that the species and size composition of piscivores differed markedly between two reef habitats where P. amboinensis was common. A cage experiment, conducted in both habitats, manipulated the sizes of predators that could access newly settled P. amboinensis to determine whether the resulting mortality of the recently settled fish was influenced by larval growth history or size at settlement. Ten days after the start of the experiment individuals that grew slowly in the second half of their larval life had been lost from most of the experimental treatments. Small fish were also selectively lost from the coarse‐mesh cage on the reef base. Significant positive relationships between pre‐ and post‐settlement growth rates were found in both habitats for the fine mesh cages, cage controls and open patch reefs. This relationship was reversed in the coarse mesh cages in both habitats. This growth compensation was facilitated through the action of a particular size range of predators, whose impact was disrupted or masked in the open treatments by the action of a diverse predator pool. The present study underscores the complexity of the processes that influence the early post‐transition growth and survival in organisms with complex life‐histories.     

Determinants of Dispersal Distance in Free-Ranging Juvenile Lizards

Dispersal of offspring from their natal site has a critical influence on individual fitness. Although the consequences of dispersal have received much theoretical attention, the determinants of dispersal remain poorly understood for many animals. To address this issue, we marked and released size‐manipulated hatchling lizards (Amphibolurus muricatus; Agamidae) over a 3‐mo period in the field to evaluate the effects of body size and the time of hatching on dispersal distance. Our mark–recapture data indicated that body size and offspring sex had little effect on distances travelled by individuals. However, the timing of hatching had a strong impact; individuals that hatched early in the season dispersed further than did those hatching late. This pattern may allow early‐hatched juveniles to disperse and secure high‐quality habitats before the arrival of later‐hatched conspecific competitors.     

Complex offspring size effects: variations across life stages and between species

Classical optimality models of offspring size and number assume a monotonically increasing relationship between offspring size and performance. In aquatic organisms with complex life cycles, the size–performance function is particularly hard to grasp because measures of performance are varied and their relationships with size may not be consistent throughout early ontogeny. Here, we examine size effects in premetamorphic (larval) and postmetamorphic (juvenile) stages of brooding marine animals and show that they vary contextually in strength and direction during ontogeny and among species. Larger offspring of the sea anemone Urticina felina generally outperformed small siblings at the larval stage (i.e., greater settlement and survival rates under suboptimal conditions). However, results differed when analyses were conducted at the intrabrood versus across‐brood levels, suggesting that the relationship between larval size and performance is mediated by parentage. At the juvenile stage (15 months), small offspring were less susceptible than large ones to predation by subadult nudibranchs and both sizes performed similarly when facing adult nudibranchs. In a sympatric species with a different life history (Aulactinia stella), all juveniles suffered similar predation rates by subadult nudibranchs, but smaller juveniles performed better (lower mortalities) when facing adult nudibranchs. Size differences in premetamorphic performance of U. felina were linked to total lipid contents of larvae, whereas size‐specific predation of juvenile stages followed the general predictions of the optimal foraging strategy. These findings emphasize the challenge in gathering empirical support for a positive monotonic size–performance function in taxa that exhibit complex life cycles, which are dominant in the sea.     

Patterns and fitness consequences of intraclutch variation in egg provisioning in tropical Australian frogs

Intraclutch variation in offspring size should evolve when offspring encounter unpredictable environmental conditions. This form of bet-hedging should maximise the lifetime reproductive success of individuals that engage it. We documented the numbers of eggs and means and variances of yolk volume in 15 frog species that occur in tropical savanna woodland. We experimentally determined the effects of initial yolk volume on larval growth patterns in four species. Intraclutch variation in yolk volume occurred to some degree in all species surveyed. Some species had very low, others had very high, intraclutch variation in yolk volume, but all species in which some clutches were highly variable also produced clutches with low variability. Species that occur in areas where the offspring environment is likely to be unpredictable had elevated levels of intraclutch variation in egg provisioning. There was no trade-off between egg size and number in any species surveyed. Under benign laboratory conditions, tadpoles from eggs with larger yolk volumes hatched at larger sizes, and these size differences persisted through a substantial proportion of the larval stage. This indicates that intraclutch variation in egg size has major offspring and thus parental fitness consequences, and is therefore a functional selection variable. This study provides evidence in support of models which predict that intraclutch variation in offspring provisioning can evolve in organisms that reproduce in unpredictable habitats.     

Egg Size Effects across Multiple Life-History Stages in the Marine Annelid Hydroides diramphus

The optimal balance of reproductive effort between offspring size and number depends on the fitness of offspring size in a particular environment. The variable environments offspring experience, both among and within life-history stages, are likely to alter the offspring size/fitness relationship and favor different offspring sizes. Hence, the many environments experienced throughout complex life-histories present mothers with a significant challenge to optimally allocate their reproductive effort. In a marine annelid, we tested the relationship between egg size and performance across multiple life-history stages, including: fertilization, larval development, and post-metamorphosis survival and size in the field. We found evidence of conflicting effects of egg size on performance: larger eggs had higher fertilization under sperm-limited conditions, were slightly faster to develop pre-feeding, and were larger post-metamorphosis; however, smaller eggs had higher fertilization when sperm was abundant, and faster planktonic development; and egg size did not affect post-metamorphic survival. The results indicate that egg size effects are conflicting in H. diramphus depending on the environments within and among life-history stages. We suggest that offspring size in this species may be a compromise between the overall costs and benefits of egg sizes in each stage and that performance in any one stage is not maximized.     

Ontogenetic changes in responses to settlement cues by Anemonefish

Population connectivity for most marine species is dictated by dispersal during the pelagic larval stage. Although reef fish larvae are known to display behavioral adaptations that influence settlement site selection, little is known about the development of behavioral preferences throughout the larval phase. Whether larvae are attracted to the same sensory cues throughout their larval phase, or exhibit distinct ontogenetic shifts in sensory preference is unknown. Here, we demonstrate an ontogenetic shift in olfactory cue preferences for two species of anemonefish, a process that could aid in understanding both patterns of dispersal and settlement. Aquarium-bred na?ve Amphiprion percula and A. melanopus larvae were tested for olfactory preference of relevant reef-associated chemical cues throughout the 11-day pelagic larval stage. Age posthatching had a significant effect on the preference for olfactory cues from host anemones and live corals for both species. Preferences of olfactory cues from tropical plants of A. percula, increased by approximately ninefold between hatching and settlement, with A. percula larvae showing a fivefold increase in preference for the olfactory cue produced by the grass species. Larval age had no effect on the olfactory preference for untreated seawater over the swamp-based tree Melaleuca nervosa, which was always avoided compared with blank seawater. These results indicate that reef fish larvae are capable of utilizing olfactory cues early in the larval stage and may be predisposed to disperse away from reefs, with innate olfactory preferences drawing newly hatched larvae into the pelagic environment. Toward the end of the larval phase, larvae become attracted to the olfactory cues of appropriate habitats, which may assist them in identification of and navigation toward suitable settlement sites.     

The adaptive significance of larval dispersal in coral reef fishes

Synopsis Coral reef fishes almost universally disperse over relatively great distances during a pelagic larval phase. Barlow (1981) suggested that this dispersal is adaptive because adult fishes inhabit a patchy, uncertain environment. This reiterated an older idea that the random extinction of local populations necessarily favours dispersal, since ultimately all populations of non-dispersers will disappear. Whereas this view is based on adult survival, we emphasize a less frequent view that substantial larval dispersal may be adaptive when offspring experience patchy and unpredictable survival in the pelagic habitat. We do not address the question of why these animals ‘broadcast’ rather than ‘brood’, but suggest that species committed to pelagic offspring will be under selection to disperse siblings to spread the risk of failure among members of a cohort. Our arguments are supported by a heuristic computer simulation.     

Size‐dependent reproductive success of wild zebrafish Danio rerio in the laboratory

Size‐dependent reproductive success of wild zebrafish Danio rerio was studied under controlled conditions in the laboratory to further understand the influence of spawner body size on reproductive output and egg and larval traits. Three different spawner size categories attained by size‐selective harvesting of the F₁‐offspring of wild D. rerio were established and their reproductive performance compared during a 5 day period. As to be expected, large females spawned more frequently and had significantly greater clutch sizes than small females. Contrary to expectations, small females produced larger eggs when measured as egg diameter with similar amounts of yolk compared to eggs spawned by large spawners. Eggs from small fish, however, suffered from higher egg mortality than the eggs of large individuals. Embryos from small‐sized spawners also hatched later than offspring from eggs laid by large females. Larval standard length (L_S)‐at‐hatch did not differ between the size categories, but the offspring of the large fish had significantly larger area‐at‐hatch and greater yolk‐sac volume indicating better condition. Offspring growth rates were generally similar between offspring from all size categories, but they were significantly higher for offspring spawned by small females in terms of L_S between days 60 and 90 post‐fertilization. Despite temporarily higher growth rates among the small fish offspring, the smaller energy reserves at hatching translated into lower condition later in ontogeny. It appeared that the influence of spawner body size on egg and larval traits was relatively pronounced early in development and seemed to remain in terms of condition, but not in growth, after the onset of exogenous feeding. Further studies are needed to explore the mechanisms behind the differences in offspring quality between large‐ and small‐sized spawners by disentangling size‐dependent maternal and paternal effects on reproductive variables in D. rerio.     

An update of the world survey of myrmecochorous dispersal distances

We update the global assessment of seed dispersal by ants and test the hypothesis that the body size of seed‐dispersing ant species varies with latitude in the same way as dispersal distance. We compiled all published data about seed dispersal distance by myrmecochory through March, 2011. We then broke the data down by vegetation type, geography and taxonomy. We also compiled data on body size (body length) of the seed‐dispersing ant species from the studies consulted. Based on 7889 observations, the mean dispersal distance was 1.99 m, although the curve has a long tail extending to 180 m. Considering the mean dispersal distance by ant species and study as independent data, the mean dispersal distance was 2.24 ± 7.19 m (n = 183). Shorter distances are associated with smaller ant species, while the tail of the dispersal curve is due to larger ant species. The mean dispersal distance of myrmecochorous seeds dispersed by ants decreased with increasing latitude, but there was no significant relationship between the body size of dispersing ant species and latitude (i.e. myrmecochorous seed‐dispersing ant species do not follow Bergmann's rule). In 1998 we made three predictions: 1) the dispersal distances of the Southern Hemisphere will decrease with as more data from mesophyllous vegetation are obtained; 2) assuming that ant nest density is higher at lower latitudes, the differences in distances between hemispheres would probably decrease with more data; and 3) numerical differences between dispersal distances in mesophyllous and sclerophyllous vegetation zones would increase with more data. The results obtained since 1998 support the only the third prediction. The dispersal distances in mesophyllous vegetation zones are shorter than in the sclerophyllous vegetation zones, and the difference between 1998 have increased. The differences in dispersal distances between hemispheres are consistent with the avoidance of parent–offspring competition (escape hypothesis).     

Relationship between morphology,dispersal and habitat distribution in three species of Libellula (Odonata: Anisoptera)

Morphology is an important determinant of flight performance and can shape species’ dispersal behaviour. This study contrasted the morphology of flight-related structures in dragonfly species with different dispersal behaviours to gain insights into the relationship between morphology and dispersal behaviour. Specifically, wing size, wing shape and thorax size were compared in three co-occurring species from different clades within the genus Libellula (Odonata: Anisoptera: Libellulidae) to assess how these morphological traits are related to differences in dispersal behaviour and to how broadly their larvae occur across a habitat gradient. Two species had broad larval habitat distributions as well as high rates and distances of dispersal. These two species had relatively larger wings and thoraces than the third species, which was found only in permanent lakes and had limited dispersal. The hind-wings of more dispersive species also had lower aspect ratios and a relatively wider basal portion of the wing than the less dispersive species. Broad hind-wings may facilitate the use of gliding flight and reduce the energetic costs of dispersal. Determining the morphological traits associated with alternative dispersal behaviours may be a useful tool to assess the differential dispersal capacities of species or populations.     

The effects of potential larval supply, settlement and post-settlement processes on the distribution of two species of filter-feeding caddisflies

1. Hydropsychid caddisfly larvae are often abundant in fast flow habitats and on highly textured substrata. Such patterns are usually inferred to result from habitat preference, but the roles of larval supply to the benthos and post‐settlement events are rarely examined for stream populations. We describe a manipulative field experiment that examined larval supply, habitat preference and post‐settlement events simultaneously for two co‐occurring species of hydropsychids. 2. Ten artificial channels were constructed in a natural riffle to create fast and slow flow habitats and within each channel we placed six artificial substrata whose surfaces had been modified to create three different texture treatments. We measured discharge through channels and monitored hydropsychid colonisation of substrata every 3–4 days. Half of the substrata had all hydropsychids and nets removed every 3–4 days (short‐term colonisation) whereas the remaining half were counted but nets and hydropsychids left attached (long‐term colonisation). Short‐term counts of nets and individuals were summed to allow comparison with long‐term colonisation substrata. 3. Smicrophylax sp. AV2 larvae were more abundant in fast flow channels than slow flow channels, but these differences were proportional to discharge through each of the channels, suggesting that supply of settlers can explain this pattern. Smicrophylax larvae were least abundant on smooth substrata, which suggests that this species selects habitats based on surface texture. Alternatively, Asmicridea sp. AV1 larvae were only found in fast flow channels and this most likely reflects an active habitat choice by this species, but there was no significant difference between different texture treatments. 4. There were no differences between summed, short‐ and long‐term counts of recruits for either species, but there were more nets than larvae, especially in slow flow channels, by the end of the experiment, suggesting that larval mortality or re‐dispersal after settlement could be considerable. 5. Our results indicate that supply, habitat selection at settlement and post‐settlement processes all contributed variously to the distribution of hydropsychid caddisfly larvae, but that each species was affected differentially by these factors. Larval supply and post‐settlement processes are rarely examined by stream researchers and our results demonstrate these factors deserve much more consideration. Calculating accurate larval supply rates to sites is challenging, but we suggest that such detailed information is necessary if we are to sort out what sets limits to distributions and the underlying population structure of stream invertebrate populations.     

COOPERATIVE BREEDING FAVORS MATERNAL INVESTMENT IN SIZE OVER NUMBER OF EGGS IN SPIDERS

The transition to cooperative breeding may alter maternal investment strategies depending on density of breeders, extent of reproductive skew, and allo‐maternal care. Change in optimal investment from solitary to cooperative breeding can be investigated by comparing social species with nonsocial congeners. We tested two hypotheses in a mainly semelparous system: that social, cooperative breeders, compared to subsocial, solitarily breeding congeners, (1) lay fewer and larger eggs because larger offspring compete better for limited resources and become reproducers; (2) induce egg size variation within clutches as a bet‐hedging strategy to ensure that some offspring become reproducers. Within two spider genera, Anelosimus and Stegodyphus, we compared species from similar habitats and augmented the results with a mini‐meta‐analysis of egg numbers depicted in phylogenies. We found that social species indeed laid fewer, larger eggs than subsocials, while egg size variation was low overall, giving no support for bet‐hedging. We propose that the transition to cooperative breeding selects for producing few, large offspring because reproductive skew and high density of breeders and young create competition for resources and reproduction. Convergent evolution has shaped maternal strategies similarly in phylogenetically distant species and directed cooperatively breeding spiders to invest in quality rather than quantity of offspring.     

Larval dispersal dampens population fluctuation and shapes the interspecific spatial distribution patterns of rocky intertidal gastropods

Many marine benthic invertebrates pass through a planktonic larval stage whereas others spend their entire lifetimes in benthic habitats. Recent studies indicate that non‐planktonic species show relatively greater fine‐scale patchiness than do planktonic species, but the underlying mechanisms remain unknown. One hypothesis for such a difference is that larval dispersal enhances the connectivity of populations and buffers population fluctuations and reduces local extinction risk, consequently increasing patch occupancy rate and decreasing spatial patchiness. If this mechanism does indeed play a significant role, then the distribution of non‐planktonic species should be more aggregated – both temporally and spatially – than the distribution of species with a planktonic larval stage. To test this prediction, we compared 1) both the spatial and the temporal abundance–occupancy relationships and 2) both the spatial and the temporal mean–variance relationships of population size across species of rocky intertidal gastropods with differing dispersive traits from the Pacific coast of Japan. We found that, compared to planktonic species, non‐planktonic species exhibited 1) a smaller occupancy rate for any given level of mean population size and 2) greater variations in population size, both spatially and temporally. This suggests that the macroecological patterns observed in this study (i.e. the abundance–occupancy relationships and mean–variance relationships of population size across species) were shaped by the effect of larval dispersal dampening population fluctuation, which works over both space and time. While it has been widely assumed that larval dispersal enhances population fluctuations, larval dispersal may in fact enhance the connectively of populations and buffer population fluctuations and reduce local extinction risks.     

A genomic approach to inferring kinship reveals limited intergenerational dispersal in the yellow fever mosquito

Understanding past dispersal and breeding events can provide insight into ecology and evolution and can help inform strategies for conservation and the control of pest species. However, parent–offspring dispersal can be difficult to investigate in rare species and in small pest species such as mosquitoes. Here, we develop a methodology for estimating parent–offspring dispersal from the spatial distribution of close kin, using pairwise kinship estimates derived from genome‐wide single nucleotide polymorphisms (SNPs). SNPs were scored in 162 Aedes aegypti (yellow fever mosquito) collected from eight close‐set, high‐rise apartment buildings in an area of Malaysia with high dengue incidence. We used the SNPs to reconstruct kinship groups across three orders of kinship. We transformed the geographical distances between all kin pairs within each kinship category into axial standard deviations of these distances, then decomposed these into components representing past dispersal events. From these components, we isolated the axial standard deviation of parent–offspring dispersal and estimated neighbourhood area (91 m), median parent–offspring dispersal distance (38 m) and oviposition dispersal radius within a gonotrophic cycle (25 m). We also analysed genetic structure using distance‐based redundancy analysis and linear regression, finding isolation by distance both within and between buildings and estimating neighbourhood size at 268 individuals. These findings indicate the scale required to suppress local outbreaks of arboviral disease and to target releases of modified mosquitoes for mosquito and disease control. Our methodology is readily implementable for studies of other species, including pests and species of conservation significance. [Correction added on 09 October 2020, after first online publication: 129 m corrected to 91 m; 75 m to 38 m; 36 m to 25 m.]     

Parentage analyses identify local dispersal events and sibling aggregations in a natural population of Millepora hydrocorals,a free‐spawning marine invertebrate

Dispersal is a critical process for the persistence and productivity of marine populations. For many reef species, there is increasing evidence that local demography and self‐recruitment have major consequences on their genetic diversity and adaptation to environmental change. Yet empirical data of dispersal patterns in reef‐building species remain scarce. Here, we document the first genetic estimates of self‐recruitment and dispersal distances in a free‐spawning marine invertebrate, the hydrocoral Millepora cf. platyphylla. Using twelve microsatellite markers, we gathered genotypic information from 3,160 georeferenced colonies collected over 27,000 m² of a single reef in three adjacent habitats in Moorea, French Polynesia; the mid slope, upper slope, and back reef. Although the adult population was predominantly clonal (85% were clones), our parentage analysis revealed a moderate self‐recruitment rate with a minimum of 8% of sexual propagules produced locally. Assigned offspring often settled at <10 m from their parents and dispersal events decrease with increasing geographic distance. There were no discrepancies between the dispersal distances of offspring assigned to parents belonging to clonal versus nonclonal genotypes. Interhabitat dispersal events via cross‐reef transport were also detected for sexual and asexual propagules. Sibship analysis showed that full siblings recruit nearby on the reef (more than 40% settled at <30 m), resulting in sibling aggregations. Our findings highlight the importance of self‐recruitment together with clonality in stabilizing population dynamics, which may ultimately enhance local sustainability and resilience to disturbance.     

Wise flies: a pre‐dispersal seed predator prefers hermaphrodites over females in the gynodioecious Polemonium foliosissimum

1. Oviposition choices can profoundly affect offspring performance. Oviposition decisions of the dipteran pre‐dispersal seed predator, Hylemya sp. (Diptera: Anthomyiidae), when choosing among sex morphs of their host‐plant—Polemonium foliosissimum Hook—were evaluated. Polemonium foliosissimum is gynodioecious, with female and hermaphrodite sex morphs that differ in flower size. 2. It was asked: Do female flies preferentially oviposit on hermaphrodite plants and, if so, are oviposition choices correlated with flower size? Is larval survivorship higher on hermaphrodite plants and, if so, is larval success correlated with flower size? Can the differences in oviposition and/or larval success be explained by slight differences in flowering phenology between the sexes? 3. Hermaphrodite flowers received 45% more Hylemya eggs than females. Although hermaphrodites had larger petals and sepals than females, egg loads were not correlated with petal or sepal size. Larval survival was 30% greater on hermaphrodites than females and higher on plants with larger sepals. However, the difference in sepal area between genders did not fully explain larval survival differences. Egg numbers declined over weeks, but differences in egg loads between the sex morphs were not attributable to a slight phenological delay of females. Larval survival declined over the season; however, larval survival differences between sex morphs were consistent. 4. Hylemya preferentially oviposited on hermaphrodites where their larvae had a significantly greater survival rate compared with females. The present results add to the knowledge that intra‐specific choices have consequences for phytophagous insects and that the relationship between antagonists and their gynodioecious host plants is complex.