Analyse expérimentale de l'isolement reproductif entre deux espèces jumelles et sympatriques d'araignées : le Lycosa thorelli (Keyserling) et le Lycosa carbonelli Costa et Capocasale

1991 ◽  
Vol 69 (7) ◽  
pp. 1768-1776 ◽  
Author(s):  
Fernando G. Costa ◽  
Gabriel Francescoli
Keyword(s):  
Sexual Pheromone ◽  
Modal Number ◽  
Copulation Pattern ◽  
Interspecific Copulation ◽  
Discrimination Level ◽  
Isolation Mechanisms ◽  
Copulatory Position

Four experimental groups were used: (A) males Lycosa thorelli × female L. thorelli; (B) male Lycosa carbonelli × female L. carbonelli; (C) Male L. thorelli × female L. carbonelli; (D) male L. carbonelli × female L. thorelli. Males were placed in a field with conspecific sexual pheromone and confronted to anesthetized virgin females. Male L. thorelli showed a greater tenacity than male L. carbonelli in the maintenance of the copulatory position. The typical copulation pattern (intraspecific groups) became atypical in interspecific groups. Only one typical interspecific copulation was observed in group C. Male L. carbonelli showed a good specific discrimination when mounting the female, while male L. thorelli showed a low discrimination level. The maintenance of the copulatory position could be determined by a modal number of ejaculations in the case of male L. carbonelli and by a modal duration in the case of male L. thorelli. Atypical copulations might indicate a mechanical incompatibility between the genitalia of the two species. Typical copulations produced offspring, indicating the absence of postcopulatory isolation mechanisms.

scholarly journals Asymmetric reproductive isolation during simultaneous reciprocal mating in pulmonates

2009 ◽  
Vol 5 (2) ◽  
pp. 240-243 ◽  
Author(s):  
Amporn Wiwegweaw ◽  
Keiichi Seki ◽  
Hiroshi Mori ◽  
Takahiro Asami
Keyword(s):  
Reproductive Isolation ◽  
The Other ◽  
Snail Species ◽  
Interspecific Mating ◽  
Premating Isolation ◽  
Reciprocal Crosses ◽  
In Captivity ◽  
Interspecific Copulation ◽  
Isolation Mechanisms ◽  
Reciprocal Mating

The generality of asymmetric reproductive isolation between reciprocal crosses suggests that the evolution of isolation mechanisms often proceeds in reciprocal asymmetry. In hermaphroditic snails that copulate simultaneously and reciprocally, asymmetry in premating isolation may not be readily detectable because the failure of the symmetric performance of courtship would prevent copulation from occurring. On the other hand, through their prolonged copulation, snails discriminate among mates when exchanging spermatophores for their benefit and thus may exhibit asymmetric reproductive isolation during interspecific mating. However, no clear case of reciprocal asymmetry has been found in reproductive isolation between snail species. Here we show a discrete difference in hybridization success between simultaneous reciprocal copulations between two species of pulmonate snails. Premating isolation of Bradybaena pellucida (BP) and Bradybaena similaris (BS) is incomplete in captivity. In interspecific copulation, BP removes its penis without transferring a spermatophore, while BS sires hybrids by inseminating BP. Thus, ‘male’ BP or ‘female’ BS rejects the other individual, while female BP and male BS accept each other, so that the two sexes of either BP or BS oppose each other in mate discrimination. Our results are a clear example of asymmetry in reproductive isolation during simultaneous reciprocal mating between hermaphroditic animals.

scholarly journals The Fungal Sexual Pheromone Sirenin Activates the Human CatSper Channel Complex

2015 ◽  
Vol 11 (2) ◽  
pp. 452-459 ◽  
Author(s):  
Shameem Sultana Syeda ◽  
Erick J. Carlson ◽  
Melissa R. Miller ◽  
Rawle Francis ◽  
David E. Clapham ◽  
...  
Keyword(s):  
Sexual Pheromone

scholarly journals A first survey of the global population size and distribution of the Scottish Crossbill Loxia scotica

2010 ◽  
Vol 21 (2) ◽  
pp. 186-198 ◽  
Author(s):  
RON W. SUMMERS ◽  
STEPHEN T. BUCKLAND
Keyword(s):  
Population Size ◽  
Habitat Management ◽  
Disjunct Distribution ◽  
Population Estimates ◽  
Modal Number ◽  
Habitat Requirement ◽  
Bird Population ◽  
Different Seasons ◽  
Common Crossbill ◽  
Global Population

SummaryA survey of Scottish Crossbills Loxia scotica was carried out in 3,506 km2 of conifer woodland in northern Scotland during January to April 2008 to provide the first estimate of the global population size for this endemic bird. Population estimates were also made for Common Crossbills L. curvirostra and Parrot Crossbills L. pytyopsittacus within this range. Crossbills were lured to systematically selected survey points for counting, sexing and recording their calls for later call-type (species) identification from sonograms. Crossbills were located at 451 of the 852 survey points, and adequate tape-recordings made at 387 of these. The Scottish Crossbill had a disjunct distribution, occurring largely within the eastern part of the study area, but also in the northwest. Common Crossbills had a mainly westerly distribution. The population size of post-juvenile Scottish Crossbills was estimated as 13,600 (95% C.I. 8,130–22,700), which will approximate to 6,800 (4,065–11,350) pairs. Common Crossbills were more abundant within this range (27,100, 95% C.I. 14,700–38,400) and Parrot Crossbills rare (about 100). The sex ratio was not significantly different from parity for Scottish Crossbills. The modal number at survey points was two but numbers were larger in January than later in the survey. The numbers and distribution of all crossbill species are likely to vary between years, depending upon the size of the cone crops of the different conifers: all were coning in 2008. Common Crossbill and Parrot Crossbill numbers will also be affected by irruptions from continental Europe. A monitoring scheme is required to detect any population trend, and further work on their habitat requirement (e.g. conifer selection at different seasons) is needed to inform habitat management of native and planted conifer forests to ensure a secure future for this endemic bird.

Self-compatible sympatric Chamaecrista (Leguminosae-Caesalpinioideae) species present different interspecific isolation mechanisms depending on their phylogenetic proximity

2013 ◽  
Vol 299 (4) ◽  
pp. 699-711 ◽  
Author(s):  
Cristiana B. N. Costa ◽  
Jorge A. S. Costa ◽  
Luciano P. de Queiroz ◽  
Eduardo L. Borba
Keyword(s):  
Isolation Mechanisms

scholarly journals There are differences in cytogenetic abnormalities among histologic subtypes of the non-Hodgkin's lymphomas

Blood ◽  
1985 ◽  
Vol 66 (6) ◽  
pp. 1414-1422 ◽  
Author(s):  
EG Levine ◽  
DC Arthur ◽  
G Frizzera ◽  
BA Peterson ◽  
DD Hurd ◽  
...  
Keyword(s):  
Chromosome Abnormality ◽  
Large Cell ◽  
Chromosome Abnormalities ◽  
Specific Chromosome ◽  
Trisomy 8 ◽  
Prognostic Information ◽  
Modal Number ◽  
Acute Leukemias ◽  
Trisomy 7 ◽  
Hodgkin's Lymphomas

Although many recurring chromosome abnormalities have been found in malignant lymphoma (ML) in recent years, their relationship to histology remains largely undefined. We have correlated, in the same tumor mass, chromosome findings with histology, defined by the International Working Formulation for Clinical Usage, in 120 patients. We find differences among histologies in the frequency of normal metaphases and the modal number of the predominant abnormal clone. In addition, most histologies have been significantly (P less than .01) associated with specific chromosome abnormalities. In particular, ML, follicular, predominantly small cleaved cell was associated with t(14;18)(q32;q21); ML, follicular, mixed small cleaved cell and large cell with t(14;18)(q32;q21) and trisomy 8; ML, follicular, predominantly large cell with trisomy 7 and breaks in 17q21-q25; ML, diffuse, mixed small cell and large cell with breaks in 11p; ML, diffuse, large cell with trisomy 21 and breaks in 2q and 9q; ML, large cell, immunoblastic with breaks at 6q21; and ML, small noncleaved cell with t(8;14)(q24;q32). Only the associations with t(14;18) and t(8;14) have been previously reported. The associated chromosome abnormality usually occurred in 30% to 70% of a given histology, raising the possibility that cytogenetics may add important prognostic information in lymphoma as it does in the acute leukemias.

Continuous, quantized and modal variation

1960 ◽  
Vol 152 (948) ◽  
pp. 397-409 ◽  
Keyword(s):  
Developmental Process ◽  
Field Size ◽  
Counting Processes ◽  
Continuous Variables ◽  
Modal Number ◽  
Integral Number ◽  
Modal Variation ◽  
Animal Populations ◽  
Almost All ◽  
Multiplicative Processes

Intraspecific variation may be continuous, or it may be quantized, if the number of structures present is always an integer. If there is some modal number of structures present in almost all individuals, variation is said to be modal. A developmental process is defined as one of ‘simple quantization’ if, first, it gives rise to an integral number of structures, and secondly, if the number of structures formed depends on the ratio between two continuous variables, for example the field size and the chemical wavelength in the model suggested by Turing (1952). Whether variation is quantized or modal will then depend on the accuracy with which these continuous variables are regulated. The larger the modal number, the more accurate must this regulation be. Data on the range of continuous variation within animal populations sug­gest that simple quantization cannot give rise to modal numbers greater than about 5 to 7. Yet modal numbers of 30 or more occur. Three processes which might account for this dis­crepancy are suggested, and evidence is presented to show that two of them occur. These are ‘multiplicative’ processes, involving successive processes of simple quantization, and ‘chemical counting’ processes, depending on qualitative differences between successively formed structures. The relevance of processes of quantization to the genesis of two-dimensional patterns is discussed.

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