Reproductive ecology of Scalesia cordata (Asteraceae), an endangered species from the Galápagos Islands

The genus Scalesia is endemic to the Galápagos Islands. Scalesia cordata is a tree occurring only in the southern part of Isabela as small, remnant populations of larger forests. We studied the reproductive ecology of a population protected in an enclosure in order to reveal the extent to which the reproductive system limits the recruitment of young individuals. Pollinator observations revealed that each capitulum received, on average, 2.5 visits per hour and exposed receptive stigmas received many pollen grains. Even so, the seed set and recruitment of trees was poor. Crossing experiments showed that S. cordata produced about twice as many fertile seeds after outcrossing than after selfing. In addition, self‐pollinated capitula flowered for a longer time than outcrossed capitula (3.8 ± 1.1 days vs. 2.1 ± 0.8 days). These results may suggest that the species is partly self‐incompatible, as other species of the genus. The small population size, with its potential derived consequences, is most certainly a prominent threat to S. cordata. The pressure from introduced plant species found in the enclosure also contributes to the seemingly poor condition of the population. To recover S. cordata, we suggest enlarging the enclosure, removing the introduced plant species and continuing to cultivate plants as a genetic reserve. Introducing new genetic material is likely to increase the seed set of the population. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 162 , 496–503.     

Pollination biology of a night‐flowering Galápagos endemic,Ipomoea habeliana (Convolvulaceae)

Ipomoea habeliana is an endemic, night‐flowering member of the Galápagos flora. Pollination experiments, flower‐visitor observations, nectar sampling, pollen transfer, and pollen to ovule ratio and pollen size studies were included in this project. The large, white flowers of this species set fruit via open pollination (55%), autonomous autogamy (51%), facilitated autogamy (91%), cross‐pollination (80%), diurnal open pollination (60%) and nocturnal open pollination (60%). Fruit set is pollen‐limited. Ants, beetles, crickets and hawk moths regularly visit the flowers. Ants are the most frequent visitors, but hawk moths are the only effective pollinators. Nectar is available throughout the night, but is most abundant early in the evening when hawk moth visits are most frequent. Experiments with fluorescent dust demonstrate intra‐ and inter‐plant pollen movement by hawk moths. Although this species is adapted for hawk moth pollination, it readily sets fruit via autonomous autogamy when no visits are made. Thus, it is concluded that it is facultatively xenogamous. Additional support for this conclusion is provided by the pollen to ovule ratio of 1407 and by the fact that the plants grow in a region that has few or no faithful pollinators. Conservation efforts for I. habeliana should include hand pollinations, which could significantly increase seed set. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 11–20.     

Pollination biology of the Galápagos endemic, Tournefortia rufo-sericea (Boraginaceae)

Tournefortia rufo-sericea is an endemic member of the Galápagos angiosperm flora. Although not uncommon within the archipelago, its status is presently listed as vulnerable and, as such, a complete knowledge of its pollination biology may prove useful in preventing its decline. Pollination experiments, flower-visitor observations, nectar and fluorescence studies, as well as pollen : ovule ratio and pollen size studies were included in this investigation. The small, white flowers of this species set fruit via open pollination (81%), autonomous self-pollination (80%), diurnal pollination (80%), and nocturnal pollination (85%). Ants are the most common visitor to the flowers of this species, primarily during the day, whereas beetles and moths make visits at night. A small amount of nectar is presumably produced, as moths are often seen probing the corollas. Experiments with fluorescent dust did not support interflower pollen movement. The pollen : ovule ratio was 4972 : 1, which suggests xenogamy, and the mean pollen size was 21 µm. Despite the pollen : ovule ratio, it appears that this species exhibits a breeding strategy of facultative autogamy, in which the majority of flowers set fruit via autonomous self-pollination, but limited outcrossing may occur when pollinators are available. Conservation efforts for T. rufo-sericea should focus on the control or eradication of exotic species.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 21–31.     

Phylogeography of palo santo trees (Bursera graveolens and Bursera malacophylla; Burseraceae) in the Galápagos archipelago

Two species of palo santo trees are distributed in the Galápagos archipelago, the native Bursera graveolens and the endemic Bursera malacophylla (Burseraceae). However, a zone of individuals morphologically intermediate between the two exists on northern Santa Cruz Island and south‐eastern Santiago Island, suggesting that they may not be reproductively isolated. Here we review the species' distributional and morphological differences and test for evidence of hybridization between the two species using DNA sequence and AFLP data. We find that the species lack distinguishing synapomorphies across the five nuclear and plastid regions examined. Population assignment tests and population genetic analyses of AFLP data indicate that genetically similar palo santo individuals (N = 87), including putative hybrids, partition into two genealogical groups that do not uniformly correspond to island‐ or taxon‐based membership. Furthermore, genotypic admixture levels among morphologically intermediate individuals do not indicate widespread hybridization. Thus, we recommend recognizing the endemic palo santo taxon as B. graveolens subspecies malacophylla (B.L.Rob.) A. Weeks & Tye comb. & stat. nov. in light of its close genetic relationship to B. graveolens subsp. graveolens and its distinctive morphology and distribution. Future research should quantify phenotypic variation in palo santo populations as another means for understanding the basis of morphological differences between the subspecies. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 161 , 396–410.     

Reproductive ecology of the endemic Lecocarpus pinnatifidus (Asteraceae) in an isolated population in the Galápagos Islands

Lecocarpus pinnatifidus is an endemic member of the Asteraceae occurring on only one island in the Galápagos archipelago. The capitula are large with female ray florets and male disc florets. They are self-compatible but this study suggests fruit set is pollen limited. Visits from Xylocopa darwini and other larger insect pollinators are rare, and small insects seem to be the main pollinators. Small insects carry few pollen grains and most likely mediate self-pollinations. Self-compatibility and seed set after selfing are the most common reproductive strategy in the Galápagos Islands and L. pinnatifidus seemingly fits well into this group.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 171–180.     

Reproductive biology of the invasive exotic shrub, Rhododendron ponticum L. (Ericaceae)

The reproductive biology of an exotic species will affect its ability to become naturalized and invasive in non-native habitats. Rhododendron ponticum is an ecologically damaging exotic weed in the British Isles, which spreads predominantly by seed. I investigated how inbreeding and outcrossing affect seed production and germination in a wild population of this species in Ireland. Experimental manipulations revealed low fruit and seed set when insects were excluded from flowers, suggesting that this species has limited capability for spontaneous autogamy. Hand-pollination treatments showed that, although flowers are self-compatible (with self and same plant pollen), higher levels of seed set occur following outcrossing (xenogamy). There was no significant difference in rate of germination of seeds from inbred or outcrossed treatments. The addition of xenogamous pollen to open flowers did not increase fruit or seed set, suggesting that flowers in this population are not pollen limited: native generalist pollinators, mainly bumblebees ( Bombus spp.), are providing an adequate pollinator service. This work demonstrates that outcrossing increases seed set and pollinators are required to facilitate this. Hence, generalist native pollinators can promote invasion by exotic plants. Native pollinators can clearly play an important part in alien species invasion.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 373–381.     

Fine‐tuning the nested structure of pollination networks by adaptive interaction switching,biogeography and sampling effect in the Galápagos Islands

The structure of pollination networks, particularly its nestedness, contain important information on network assemblages. However, there is still limited understanding of the mechanisms underlying nested pollination network structures. Here, we investigate the role of adaptive interaction switching (AIS), island area, isolation, age and sampling effort in explaining the nestedness of pollination networks across ten Galápagos Islands. The AIS algorithm is inspired by Wallace's elimination of the unfit, where a species constantly replaces its least profitable mutualistic partner with a new partner selected at random. To explain network structures, we first use a dynamic model that includes functional response of pollination and AIS, with only species richness and binary connectance as input (hereafter the AIS model). Thereafter, other explanatory variables (isolation, area, age and sampling effort) were added to the model. In four out of ten islands, the pollination network was significantly nested, and predictions from the AIS model correlated with observed structures, explaining 69% variation in nestedness. Overall, in terms of independent contribution from hierarchical partitioning of variation in observed nestedness, the AIS model predictions contributed the most (37%), followed by sampling effort (28%) and island area (22%), with only trivial contributions from island isolation and age. Therefore, adaptive switching of biotic interactions seems to be key to ensure network function, with island biogeographic factors being only secondary. Although large islands could harbour more diverse assemblages and thus foster more nested structures, sufficient sampling proves to be essential for detecting non‐random network structures.     

Reproductive biology of Ferocactus recurvus (Mill.) Borg subsp. recurvus (Cactaceae) in the Tehuacán‐Cuicatlán Valley,Mexico

• Mexico has one of the highest diversities of barrel cacti species worldwide; however, all are threatened and require conservation policies. Information on their reproductive biology is crucial, but few studies are available. Ferocactus recurvus subsp. recurvus is a barrel cactus endemic to the Tehuacán‐Cuicatlán Valley. Our research aimed to characterise its floral and pollination biology. We hypothesised bee pollination, as suggested by its floral morphology and behaviour, and self‐incompatibility, like most barrel cacti studied.
• Three study sites were selected in the semiarid Zapotitlán Valley, Mexico. We examined 190 flowers from 180 plants to determine: morphometry and behaviour of flowers, flower visitors and probable pollinators, and breeding system.
• Flowers showed diurnal anthesis, lasting 2–5 days, the stigma being receptive on day 2 or 3 after the start of anthesis. Flowers produced scarce/no nectar and main visitors were bees (Apidae), followed by flies (Muscidae), ants (Formicidae), thrips (Thripidae) and hummingbirds (Throchilidae); however, only native bees and occasionally wasps contacted the stigma and anthers. Pollination experiments revealed that this species is self‐incompatible and xenogamous. In natural conditions, fruit set was 60% and cross‐pollination fruit set was 100%. Percentage seed germination resulting from cross‐pollination was higher than in the control treatment.
• Our results provide ecological information for conservation programmes to ensure a high probability of breeding and seed production in natural populations of F. recurvus.

     

Reproductive biology of the rare and endangered Banksia brownii Baxter ex R. Br. (Proteaceae)

Abstract Banksia brownii is an endangered species, now limited to ～ 15 disjunct populations in southwestern Western Australia. Data on flowering phenology, plant size, fruit set, pollination and the mating system were gathered for two of these populations between March and October 1993. Flowering for both populations followed a similar pattern, with open flowers first evident in April, and the number of inflorescences with open flowers peaking in June. At both locations, trees differed considerably with respect to their size, the total number of inflorescences produced and the length of their flowering season. Fruiting success was typically low, with approximately half of all inflorescences failing to develop into infructescences. Only 1. 8% of the flowers originally present on inflorescences developed into follicles. The distribution of follicles along each infructescence was non-random, with most forming in the middle third of the infructescence for reasons relating to nutrient supply and pollinator behaviour. More flowers opened during the day than at night, although pollen was lost from individual flowers during both periods. Honeyeaters such as Phylidonyris novaehollandiae were common at the two study sites, and often carried large loads of B. brownii pollen. Though less frequently caught, the nocturnal mammals Rattus fuscipes and Tarsipes rostratus also bore substantial amounts of pollen. Most inflorescences from which these mammals and birds were excluded remained barren. Fruiting success was further reduced when invertebrates such as Apis mellifera were also prevented from visiting inflorescences. The ability of B. brownii to set at least some fruit in the absence of biotic poli-nators indicates that the species is partially self-compatible. Honeyeaters foraged preferentially at inflorescences with one to two thirds of their flowers open, probing mainly along the ‘advancing front’ of open flowers. These animals moved more frequently between inflorescences on the same plant than between those on different plants, and were often recaptured in the same locations. Mammals also appeared to be sedentary. Both B. brownii populations had mixed mating systems, with genetically determined outcrossing rates of ～0.7. The unusually high level of selfing in each population is presumably a reflection of the species’ self-compatibility and the foraging behaviour of its pollinators.     

Isolation and characterization of microsatellite loci in the Galápagos Opuntia weevil Gerstaeckeria galapagoensis (Coleoptera,Curculionidae)

Five microsatellite loci were isolated from the Galápagos weevil Gerstaeckeria galapagoensis. Polymorphism ranged from two to seven alleles, and observed and expected heterozygosities ranged from 0.286 to 0.917 and 0.254 to 0.683, respectively.     

The effects of host plant phenology on the demography and population dynamics of the leaf-mining moth, Cameraria hamadryadella (Lepidoptera: Gracillariidae)

Abstract.

• 1 We examined the effects of variation in the timing of spring leaf production and autumn leaf fall on the survival, mortality and abundance of Cameraria hamadryadella on Quercus alba and Q.macrocarpa.
• 2 We monitored and manipulated the timing of foliation on field and potted Q.alba trees and observed the abundance of C.hamadryadella on those trees. We also monitored and manipulated the timing of leaf fall on Q.alba and Q.macrocarpa trees in the field and observed its effects on survival, mortality and abundance of C.hamadryadella.
• 3 Variation in the timing of spring leaf production has no effect on C. hamudryadella abundance. However, a warm winter and spring in 1991 led to accelerated development and the imposition of a facultative third generation in one out of ten years of observation.
• 4 In 1989, leaves fell relatively early and leaf fall in the autumn accounted for more than 50% of the mortality of C.hamudryadella. in 1990 and 1991 leaves fell relatively late and leaf fall induced mortality was substantially reduced and overwinter survival was markedly increased.
• 5 The abundance of C.hamadryadella remained constant in the spring and summer of 1990 following the previous autumn's relatively early leaf fall, but increased by 10-fold in the spring of 1991 following the relatively late leaf fall of autumn 1990. The abundance of C.hamadryadella also increased 4-fold between the summer of 1991 and the spring of 1992 after another autumn of relatively late leaf fall. We attribute these increases in abundance in part to reduced mortality because of later leaf fall.
• 6 Variation in the timing of autumn leaf fall may be responsible for initiating outbreaks of C.hamadryadella.

     

Male reproductive success and its behavioural correlates in a polygynous mammal,the Galápagos sea lion (Zalophus wollebaeki)

Sexual selection theory predicts competitive males and choosy females. Nevertheless, since molecular marker‐based studies, paternity outside the expected mating patterns has increasingly been described. Even in highly polygynous systems, where paternity is expected to be strongly skewed towards large, dominant males, alternative mating tactics have been suggested. We examined reproductive success in the polygynous Galápagos sea lion (Zalophus wollebaeki). Semiaquatic territoriality allows females to move freely and may lower the degree of polygyny otherwise suggested by both territorial behaviour and strong sexual dimorphism. We assigned paternities with 22 microsatellites and analysed how male reproductive success was related to size, dominance status, intra‐sexual agonistic behaviour, proximity to females, and attendance in the colony. Male behaviour was consistent across two seasons for all parameters under consideration. Attendance was by far the most important determinant of paternal success. Skew in reproductive success towards large, dominant males was weak and dominance status played no role. This appears to be caused by an extremely long reproductive season lasting five or more months, making it difficult for any male to monopolize receptive females. Females seem to choose displaying males that were present in the colony for a long time rather than dominance per se. Sexual dimorphism in Galápagos sea lions may thus be more influenced by selection for fasting than fighting ability. Our data provide further evidence for alternative mating tactics, as several males gained relatively high reproductive success despite short attendance and hardly any involvement in agonistic interactions.     

Genetic and morphometric evidence on a Galápagos Island exposes founder effects and diversification in the first‐known (truly) feral western dog population

Domesticated animals that revert to a wild state can become invasive and significantly impact native biodiversity. Although dogs can be problematic locally, only the Australasian dingo is known to occur in isolation from humans. Western dogs have experienced more intense artificial selection, which potentially limits their invasiveness. However, feral dogs eradicated from Isabela Island, Galápagos in the 1980s could be the first‐known exception. We used DNA and morphometric data from 92 of these dogs to test the hypotheses that (i) these dogs persisted independently of humans for up to a century and a half since descending from a handful of dogs introduced in the early 1800s, vs. (ii) similarly to other western feral dog populations, they reflected continuous recruitment of strays from human settlements on a portion of the Island. We detected one dominant maternal lineage and one dominant paternal lineage shared by the three subpopulations, along with low autosomal genetic diversity, consistent with the hypothesized common origins from a small founder population. Genetic diversity patterns among the three island subpopulations were consistent with stepping‐stone founder effects, while morphometric differentiation suggested rapid phenotypic divergence, possibly due to drift and reinforced by selection corresponding to distinct microclimates and habitats on Isabela. Despite the continued presence of free‐ranging dogs in the vicinity of settlements on Isabela and other Galápagos Islands, feral populations have not reestablished in remote areas since the 1980s, emphasizing the rarity of conditions necessary for feralization of modern western dogs.     

Extinction,reintroduction, and restoration of a lizard meta‐population equilibrium in the missouri ozarks

In this issue of Molecular Ecology, Neuwald & Templeton (2013) report on a 22‐year study of natural populations of Collared Lizards (Crotaphytus collaris) that evolved on isolated on rock outcrops (‘glades’) in the Ozark Mountains in eastern Missouri. This ecosystem was originally maintained by frequent fires that kept the forest understory open, but fire‐suppression was adopted as official policy in about 1945, which led to a loss of native biodiversity, including local extinctions of some lizard populations. Policies aimed at restoring biodiversity included controlled burns and re‐introductions of lizards to some glades, which began in 1984. Populations were monitored from 1984–2006, and demographic and genetic data collected from 1 679 lizards were used to documents shifts in meta‐population dynamics over four distinct phases of lizard recovery: 1–an initial translocation of lizards drawn from the same source populations onto three glades that were likely part of one meta‐population; 2–a period of isolation and genetic drift associated with the absence of fires; 3–a period of rapid colonization and population increase following restoration of fire; and 4–stabilization of the meta‐population under regular prescribed burning. This study system thus provides a rare opportunity to characterize the dynamics of a landscape‐scale management strategy on the restoration of the meta‐population of a reintroduced species; long‐term case studies of the extinction, founding, increase, and stabilization of a well‐defined meta‐population, based on both demographic and population genetic data, are rare in the conservation, ecological, and evolutionary literature.     

Development of primers to characterize the mitochondrial control region of Galápagos land and marine iguanas (Conolophus and Amblyrhynchus)

Primers were developed for the amplification and sequencing of the mitochondrial control region of Galápagos land (Conolophus) and marine (Amblyrhynchus) iguanas. Sequences were obtained for four land iguana samples from two islands and for 28 marine iguana samples from three islands. A series of 70–80 bp tandem repeats adjacent to the control region are described and preliminary quantification of intra‐ and interspecific sequence divergence is included.     

Pheromone trap catches of the olive moth, Prays oleae (Bern.) (Lep., Plutellidae) in relation to olive phenology and degree-day models

Abstract:  The population dynamics of the olive moth, Prays oleae (Bern) (Lep., Plutellidae) was monitored using pheromone traps containing (Z)-7-tetradecenal, from 2000 to 2002 in abandoned and commercial olive groves of Bursa in north-western Turkey. The carpophagous generation lasted significantly longer than the phyllophagous generation. The degree-days required for the anthophagous generation were significantly shorter than that for the phyllophagous and carpophagous generations. The relationship between temperature accumulations and pheromone trap captures of male P. oleae in Bursa olive groves showed a significant sigmoid relationship for the phyllophagous and anthophagous flights. Although there was generally a linear relationship between cumulative male catch and olive tree phenology, the use of the prediction model for insecticide treatments was insufficient. Cumulative male catch–degree days together with the olive tree phenology model can be used as a forecasting method for proper timing of insecticide applications against anthophagous and carpophagous larvae in olive groves.