Hop tree (Ptelea trifoliata) in Canada: population and reproductive biology of a rare species

1985 ◽  
Vol 63 (11) ◽  
pp. 1928-1935 ◽  
Author(s):  
John D. Ambrose ◽  
Peter G. Kevan ◽  
Randy M. Gadawski
Keyword(s):  
Sex Ratio ◽  
Rare Species ◽  
Lake Erie ◽  
Sexual Expression ◽  
Large Area ◽  
Natural Distribution ◽  
Dioecious Species ◽  
Visitation Rates ◽  
Insect Visitation ◽  
Disturbed Habitats

In Canada, Ptelea trifoliata L. (Rutaceae) is restricted in its natural distribution primarily to the Lake Erie shoreline. Although it is locally successful as a colonizing species, it appears inhibited from either exploiting a large area of shoreline habitat or extending its range inland. The morphological descriptions of the hop tree's sexual expression have been ambiguous; however, our observations show this species to be clearly dioecious, with only about 2% of the otherwise male plants producing a few hermaphroditic flowers, and fruit. The sex ratio is strongly skewed toward the males, which produce more and showier inflorescences than female plants. Despite this, the insect visitation rates are not significantly different between the sexes. For pollination, the hop tree is a polyphilic generalist, dependent on a diverse array of insects, including short-tongued bees, wasps, and flies. It is totally dependent on wind-dispersed seeds for establishment, lacking the ability to grow clonally. In a dioecious species of disturbed habitats, this is exceptional.

scholarly journals Busy Bees: Variation in Insect Flower-Visiting Rates across Multiple Plant Species

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Margaret J. Couvillon ◽  
Chandra M. Walter ◽  
Eluned M. Blows ◽  
Tomer J. Czaczkes ◽  
Karin L. Alton ◽  
...  
Keyword(s):  
Apis Mellifera ◽  
Honey Bee ◽  
Plant Species ◽  
Honey Bees ◽  
Bumble Bees ◽  
The Other ◽  
Insect Diversity ◽  
Visitation Rates ◽  
Insect Visitation ◽  
Flower Visiting

We quantified insect visitation rates by counting how many flowers/inflorescences were probed per unit time for five plant species (four native and one garden: California lilac, bramble, ragwort, wild marjoram, and ivy) growing in Sussex, United Kingdom, by following individual insects (n=2987) from nine functional groups (honey bees (Apis mellifera), bumble bees (Bombusspp.), hoverflies, flies, butterflies, beetles, wasps, non-Apidae bees, and moths). Additionally, we made a census of the insect diversity on the studied plant species. Overall we found that insect groups differed greatly in their rate of flower visits (P<2.2e-16), with bumble bees and honey bees visiting significantly more flowers per time (11.5 and 9.2 flowers/minute, resp.) than the other insect groups. Additionally, we report on a within-group difference in the non-Apidae bees, where the genusOsmia, which is often suggested as an alternative to honey bees as a managed pollinator, was very speedy (13.4 flowers/minute) compared to the other non-Apidae bees (4.3 flowers/minute). Our census showed that the plants attracted a range of insects, with the honey bee as the most abundant visitor (34%). Therefore, rate differences cannot be explained by particular specializations. Lastly, we discuss potential implications of our conclusions for pollination.

scholarly journals Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination?

2013 ◽  
Vol 280 (1772) ◽  
pp. 20132460 ◽  
Author(s):  
Timothy S. Mitchell ◽  
Jessica A. Maciel ◽  
Fredric J. Janzen
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Nest Site ◽  
Sex Ratios ◽  
Temperature Dependent ◽  
Dioecious Species ◽  
Offspring Sex Ratio ◽  
Nest Sites ◽  
Offspring Sex ◽  
Nest Site Choice

Evolutionary theory predicts that dioecious species should produce a balanced primary sex ratio maintained by frequency-dependent selection. Organisms with environmental sex determination, however, are vulnerable to maladaptive sex ratios, because environmental conditions vary spatio-temporally. For reptiles with temperature-dependent sex determination, nest-site choice is a behavioural maternal effect that could respond to sex-ratio selection, as mothers could adjust offspring sex ratios by choosing nest sites that will have particular thermal properties. This theoretical prediction has generated decades of empirical research, yet convincing evidence that sex-ratio selection is influencing nesting behaviours remains absent. Here, we provide the first experimental evidence from nature that sex-ratio selection, rather than only viability selection, is probably an important component of nest-site choice in a reptile with temperature-dependent sex determination. We compare painted turtle ( Chrysemys picta ) neonates from maternally selected nest sites with those from randomly selected nest sites, observing no substantive difference in hatching success or survival, but finding a profound difference in offspring sex ratio in the direction expected based on historical records. Additionally, we leverage long-term data to reconstruct our sex ratio results had the experiment been repeated in multiple years. As predicted by theory, our results suggest that sex-ratio selection has shaped nesting behaviour in ways likely to enhance maternal fitness.

scholarly journals Rotating Arrays of Orchid Flowers: A Simple and Effective Method for Studying Pollination in Food Deceptive Plants

Diversity ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 286 ◽  
Author(s):  
Daniela Scaccabarozzi ◽  
Andrea Galimberti ◽  
Kingsley W. Dixon ◽  
Salvatore Cozzolino
Keyword(s):  
Field Observations ◽  
Pollination Success ◽  
Visitation Rates ◽  
Visitation Frequency ◽  
Pollination Mechanisms ◽  
Behavioural Patterns ◽  
Insect Visitation ◽  
Southwest Australia ◽  
First Time ◽  
Effective Pollinators

Floral deception has been observed in several genera in angiosperms, but is most common in the Orchidaceae. Pollination mechanisms in food deceptive plants are often difficult to assess, as visitation frequency by insects requires numerous hours of field observations to ascertain. Here, for the first time, we describe in detail and validate a simple and effective method that extends previous approaches to increase the effectiveness of pollination studies of food deceptive orchids. We used an orchid of southwest Australia, Diuris brumalis (Orchidaceae), that visually mimics model plants belonging to the genus Daviesia (Faboideae). Arrays of orchid flowers were placed and moved systematically in proximity to model plants, resulting in rapid attraction of the pollinators of D. brumalis. We compared pollinaria removal (as an indicator of pollination success) in naturally growing orchids with pollinaria removal in arrays of orchid flowers in the same sites. We showed that the proposed method greatly enhances pollinator attractiveness in food deceptive systems with very low pollination rates, and we compared its efficiency with other similar methods. The approach can be used for observing pollinator behavioural patterns and confirming effective pollinators for food deceptive species with low insect visitation rates.

scholarly journals Sexual ratio and floral biology of the dioecious Neea theifera Oerst. (Nyctaginaceae) in a cerrado rupestre of central Brazil

2011 ◽  
Vol 25 (4) ◽  
pp. 785-792 ◽  
Author(s):  
Felipe Wanderley Amorim ◽  
Clesnan Mendes-Rodrigues ◽  
Pietro Kiyoshi Maruyama ◽  
Paulo Eugênio Oliveira
Keyword(s):  
Resource Allocation ◽  
Sex Ratio ◽  
Reproductive Biology ◽  
Reproductive Strategy ◽  
Pollen Viability ◽  
Floral Biology ◽  
Pollinator Limitation ◽  
Dioecious Species ◽  
Male And Female ◽  
Pollination Success

Dioecy is characterized by a complete separation of sexual functions on male and female plants. It has evolved many times in flowering plants and is widespread among distinct Angiosperm families. It is viewed as a reproductive strategy to reduce endogamy, and to promote optimal resource allocation between male and female sexual functions. Neea theifera is a common species in Cerrado, neotropical savannas in Brazil, but information regarding its reproductive biology is still incomplete. In order to investigate how environmental conditions possibly affect this dioecious species, we studied its floral biology, sex ratio and spatial distribution of sexual morphs along a soil-altitudinal gradient. The sex ratio did not significantly deviate from the expected 1:1 ratio. However, flower abundance in the population was significantly biased towards staminate flowers. Female individuals were larger than male individuals and plant size was negatively correlated with altitude, but did not differ between sexual morphs. The population did not show spatial segregation of sexes and male individuals were sexually mature earlier than female ones. Staminate flowers were larger than pistillate flowers and presented high pollen viability. Meliponini bees, small flies and thrips were potential pollinators, but pollination success was very low. Dioecy in N. theifera corroborates many general features of this reproductive strategy, such as woody habit, inconspicuous flowers, pollination by small generalist insects and differential resource allocation between male and female plants. However, reproduction in this species seems to be impaired by pollinator limitation. The results showed that the soil-altitude gradient influenced the growth pattern of the species and may play an important role in its reproductive biology but did not affect dioecy directly.

Insect visitation rates and foraging patterns differ in androdioecious and hermaphrodite-only populations of Laguncularia racemosa (Combretaceae) in Florida

2012 ◽  
Vol 28 (4) ◽  
pp. 343-351 ◽  
Author(s):  
Carol L. Landry ◽  
Beverly J. Rathcke
Keyword(s):  
Apis Mellifera ◽  
Mathematical Models ◽  
Breeding System ◽  
Laguncularia Racemosa ◽  
Foraging Patterns ◽  
Visitation Rates ◽  
Self Pollination ◽  
Insect Visitation ◽  
Relative Abundances

Abstract:Insect-pollinated Laguncularia racemosa has a variable breeding system; some populations are androdioecious, with male and hermaphroditic plants, while others lack male plants. We observed the foraging behaviours of insects in three androdioecious and three hermaphrodite-only populations of L. racemosa in Florida. In each population, insect visitation rates were estimated from 30–108 timed intervals. We recorded the number of flowers visited by 144–224 insects during foraging bouts made to 15–40 male and hermaphroditic plants. Male plants in androdioecious populations had significantly more visitors than hermaphroditic plants, increasing the number of vectors carrying pollen from male plants. Further, many insects visited few flowers during foraging bouts, which should increase outcrossing frequency. According to mathematical models, male plants benefit from these combined factors. Plants in hermaphrodite-only populations had significantly more visitors than hermaphroditic plants in androdioecious populations. Proportionately more insects visited many flowers during foraging bouts in hermaphrodite-only versus androdioecious populations. The increased likelihood of geitonogamous self-pollination could help explain the lack of male plants in hermaphrodite-only populations. Differences in pollinator assemblages and the relative abundances of several species were responsible for differences in foraging behaviours: Apis mellifera, Bombus sp., Melissodes sp., Xylocopa sp., Euodynerus sp. and a calliphorid species.

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