Floral syndrome in Amelanchier nantucketensis (Rosaceae). I. Floral density, bee activity, and characterization of andropetaly

1997 ◽  
Vol 75 (11) ◽  
pp. 1851-1859 ◽  
Author(s):  
Alison C. Dibble ◽  
Francis A. Drummond

The clonal shrub Amelanchier nantucketensis is andropetalous; a variable number of petals as well as normal anthers both bear germinable pollen. To determine whether floral density associated with andropetaly is related to activity of native bees on flowers, we compared Amelanchier nantucketensis to Amelanchier humilis and Amelanchier stolonifera, which have sterile petals. In samples from four Maine sites, floral density in Amelanchier nantucketensis was 30.3% greater than that for Amelanchier humilis and 39.5% greater than that for Amelanchier stolonifera; in Amelanchier nantucketensis, flowers were more numerous per cubic metre and distance between flowers was shorter. There was a significant correlation across all sites and species between the number of flowers per plant and number of inflorescences visited per bee in 10 min (r = 0.711, p = 0.0001). Statistical t tests separated Amelanchier nantucketensis from both Amelanchier humilis and Amelanchier stolonifera by plant height, nearest stem, nearest flower, and number of inflorescences visited per bee during 10 min. Plant species classification in a canonical discriminant analysis was 83–93% correct with four plant variables, namely distance to nearest flower, distance to nearest inflorescence, plant width, and plant height. Our findings support optimal foraging theory in that bee visits increase with floral density in these Amelanchier species. Key words: Amelanchier, andropetaly, bees, floral density, morphology, Maine.

Author(s):  
Poppy M. Jeffries ◽  
Samantha C. Patrick ◽  
Jonathan R. Potts

AbstractMany animal populations include a diversity of personalities, and these personalities are often linked to foraging strategy. However, it is not always clear why populations should evolve to have this diversity. Indeed, optimal foraging theory typically seeks out a single optimal strategy for individuals in a population. So why do we, in fact, see a variety of strategies existing in a single population? Here, we aim to provide insight into this conundrum by modelling the particular case of foraging seabirds, that forage on patchy prey. These seabirds have only partial knowledge of their environment: they do not know exactly where the next patch will emerge, but they may have some understanding of which locations are more likely to lead to patch emergence than others. Many existing optimal foraging studies assume either complete knowledge (e.g. Marginal Value Theorem) or no knowledge (e.g. Lévy Flight Hypothesis), but here we construct a new modelling approach which incorporates partial knowledge. In our model, different foraging strategies are favoured by different birds along the bold-shy personality continuum, so we can assess the optimality of a personality type. We show that it is optimal to be shy (resp. bold) when living in a population of bold (resp. shy) birds. This observation gives a plausible mechanism behind the emergence of diverse personalities. We also show that environmental degradation is likely to favour shyer birds and cause a decrease in diversity of personality over time.


Nature ◽  
1977 ◽  
Vol 268 (5621) ◽  
pp. 583-584 ◽  
Author(s):  
John Krebs

1986 ◽  
Vol 6 (3) ◽  
pp. 933-941
Author(s):  
J E Garrett ◽  
D Carroll

A family of transposable genetic elements in the genome of the frog, Xenopus laevis, is described. They are designated Tx1. Transposability of the elements was deduced by characterization of a chromosomal locus which is polymorphic for the presence or absence of a Tx1 element. Nucleotide sequence analysis suggested that Tx1 elements show target site specificity, as they are inserted at the pentanucleotide TTTAA in all four cases that were examined. The elements appear to have 19-base-pair (bp) inverted terminal repeats, and they are flanked by 4-bp target duplications (TTAA), although the possibility that they do not create target site duplications is discussed. Tx1 elements have several unusual characteristics: the central portion of each element is comprised of a variable number of two types of 393-bp repeating units; the rightmost 1,000 bp of the element contains separate regions potentially capable of forming bends, left-handed Z-form DNA, and alternative stem-loop structures. Comparisons among single frogs suggest that germ line transposition is relatively infrequent and that variations in numbers of internal repeats accumulate quite slowly at any locus.


2016 ◽  
Vol 112 ◽  
pp. 127-138 ◽  
Author(s):  
Dahlia Foo ◽  
Jayson M. Semmens ◽  
John P.Y. Arnould ◽  
Nicole Dorville ◽  
Andrew J. Hoskins ◽  
...  

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