Can the problem of hybridization in threatened species be evaluated using a fieldwork research? A case study in snapdragons

Hybridization, natural or artificial, is considered disadvantageous for species biodiversity when it threatens the population integrity of endangered species. Frequently, studies investigating whether hybridization poses a legitimate risk to rare species are based on genetic data obtained in molecular biology laboratories. In this study, we used field research to approach the problem that hybridization could cause for the viability of a population of a rare species and to be able to propose the most appropriate initial conservation strategy. Specifically, using the model genus Antirrhinum, the reproductive barriers between the rare A. pulverulentum and its common congener A. litigiosum have been analysed under the reproductive isolation index (RI). A. pulverulentum had a high value of total RI, indicating that there are barriers to gene flow from A. litigiosum towards this species, and also had a high value for the intrinsic RI, reflecting a low inherent capacity for production of hybrid plants; in addition, the possibility of successful backcrosses between this species with hybrids produced from A. litigiosum ovules were low, given the high intrinsic RI of A. litigiosum. These data indicate the current existence of strong and permanent barriers to hybridization between the two species, suggesting that hybridization does not seem to be a serious problem for the conservation of A. pulverulentum in the studied population, nor for the near future. This study shows how the RI index can provide useful information for conservation purposes and proposes different management recommendations.     

Correlation between two components of parental investment: nest defence intensity and nestling provisioning effort of willow tits

Nest defence intensity and nestling provisioning effort of female willow tits (Parus montanus) were significantly correlated at the end of nestling period: well-fed young were defended most intensely. Increased effort was rewarded, since broods with the highest female per-offspring provisioning rates were the most likely to produce local recruits. This suggests that the feeding ability is an important cue for parental investment decisions, at least in a species like the willow tit which has adopted the clutch adjustment strategy. Thus, the most valuable broods would not necessarily be the largest ones, but the ones in which the original number of young could be fed most adequately. However, no associations were found between the level of parental effort and offspring weight, size or condition, nor did the broods producing recruits differ from other broods in timing of breeding or number and size of offspring. The female behaviour may suggest that they invest the most time, energy and risk in the young whose chances of joining the winter flock are the best. The first well-fed young also gain an advantage of prior residency in joining the flock. The first to join normally obtain higher social status, and hence better winter survival, than latecomers. The corresponding patterns in male parental investment behaviour were weak or absent, which suggested that the male effort was affected by the female behaviour. Males seemed to invest in nestling provisioning in such a way as to supplement the female effort. During nest defence action males also seemed to invest in protection of females against predation.     

Curculionid beetles in aborted flower buds and immature fruits of <Emphasis Type="Italic">Ceiba</Emphasis><Emphasis Type="Italic">pentandra</Emphasis> (Bombacaceae)

We determined the incidence of curculionid beetles of the genus Lonchophorus on aborted and not aborted flower buds and developing fruits of the tree Ceiba pentandra in southeastern Costa Rica. Beetle larvae were found in reproductive parts of all trees sampled trees. The frequency of beetle larvae was greater in aborted buds and immature fruits. A positive correlation between larvae development and flower bud development indicates that female oviposition occurred in an early flower developmental stage and time until bud abortion is variable. Weevil herbivory could be considered as one of the main factors that cause flower bud and fruit abortion in C. pentandra.

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Resumen Determinamos la incidencia de curculiónidos del género Lonchophorus en botones florales y frutos inmaduros tanto abortados como no abortados en el árbol Ceiba pentandra en el SE de Costa Rica. Las larvas de curculiónidos fueron encontradas en todos los árboles muestreados. La frecuencia de larvas fue mayor en botones y frutos abortados. Una correlación positiva entre el desarrollo larval y el desarrollo del botón indica que la oviposición ocurre en una fase temprana de este y que el tiempo hasta el aborto es variable. La herbivoría por larvas de curculiónidos puede ser uno de los factores más importantes en el aborto de botones y frutos inmaduros en C. pentandra.

     

The Analysis of Partial Diallel Crosses

The analysis of offsprings from the partial diallel crosses is presented. In considered type of crossing, p parental forms into H separate groups are devided. Single crosses among parental forms, from separate groups only, are performed. The analysis for experiments laid out in efficiency balanced block designs is given.     

A general approach to the concept of varietal ability for synthetic varieties

Summary Genetic effects for varietal value are defined at the level of the population of k-parent synthetic varieties. A simple expression for the total variance among synthetics arises directly from these definitions. A general expression for the covariance among related synthetics is given. Genetic effects are also defined in a completely general way so as to allow for any system of testing and used to derive an expression for the genetic advance in recurrent selection for varietal value. Covariances between relatives evaluated in the system of testing and in varietal combination are introduced, allowing a direct expression of the genetic advance in varietal development when parents are selected either individually or in groups. Some general implications for plant breeding are outlined.Dedicated to Professor F.W. Schnell on the occasion of his 65th birthday     

Habitat availability,social attraction and nest distribution patterns in longear sunfish (Lepomis megalotis peltastes)

Synopsis Two forces, limited availability of preferred habitat and social attraction between conspecifics were hypothesized to explain nest aggregation in male longear sunfish. In the laboratory, males cluster their nests within a small segment of a much larger uniform area of nesting habitat. In the field, large areas of unused habitat suitable for nesting were found, suggesting that nesting aggregations are not formed as a result of limited preferred habitat. Males appear to be socially attracted during breeding, and social nesting presumably is a successful reproductive strategy for at least a portion of the population.     

Sex differences in leg dexterity are not present in elite athletes

We studied whether the time-varying forces that control unstable foot–ground interactions provide insight into the neural control of dynamic leg function. Twenty elite (10 F, 26.4 ± 3.5 yrs) and 20 recreational (10 F, 24.8 ± 2.4 yrs) athletes used an isolated leg to maximally compress a slender spring designed to buckle at low forces while seated. The foot forces during the compression at the edge of instability quantify the maximal sensorimotor ability to control dynamic foot–ground interactions. Using the nonlinear analysis technique of attractor reconstruction, we characterized the spatial (interquartile range IQR) and geometric (trajectory length TL, volume V, and sum of edge lengths SE) features of the dynamical behavior of those force time series. ANOVA confirmed the already published effect of sex, and a new effect of athletic ability, respectively, in TL (p = 0.014 and p < 0.001), IQR (p = 0.008 and p < 0.001), V (p = 0.034 and p = 0.002), and SE (p = 0.033 and p < 0.001). Further analysis revealed that, for recreational athletes, females exhibited weaker corrective actions and greater stochasticity than males as per their greater mean values of TL (p = 0.003), IQR (p = 0.018), V (p = 0.017), and SE (p = 0.025). Importantly, sex differences disappeared in elite athletes. These results provide an empirical link between sex, athletic ability, and nonlinear dynamical control. This is a first step in understanding the sensorimotor mechanisms for control of unstable foot–ground interactions. Given that females suffer a greater incidence of non-contact knee ligament injuries, these non-invasive and practical metrics of leg dexterity may be both indicators of athletic ability, and predictors of risk of injury.     

Nutritional status influences reproductive seasonality in Creole goats: 1. Ovarian activity during seasonal reproductive transitions

The objective was to determine the effect of body energy stores, evaluated by a body mass index (BMI), and food intake (FI), on the length of the anovulatory period and ovarian activity during the seasonal reproductive transitions in Creole goats. Non-pregnant, non-lactating Creole goats (n = 28) were fed to induce two different BMI conditions: Greater (GBMI; n = 15), and Lesser (LBMI; n = 13). Each BMI group was divided into two sub-groups, which were either feed restricted (FR) or non-feed restricted (NFR). Goats in the NFR groups received a diet containing 100% of the daily maintenance requirements (basal diet), while restricted goats were subjected to alternated periods, receiving 100% (11 d) and 60% (10 d) of the basal diet, during the entire experimental period. The experiment started after does were treated to synchronize time of estrus. Serum progesterone was determined in samples obtained twice a week, and used as a criterion for determining ovulations. During the transition to the anovulatory period three transrectal ovarian ultrasonographic scans were performed in a sub-group of 12 goats (n = 3 for each treatment combination). The diameter of the largest follicle (LFD) and the total number of antral follicles ≥2 mm (TAF) were recorded. Ultrasonographic ovarian scans were performed at 21, 42 and 63 days after the beginning of the experiment, concurrently with the end of each feed restriction period. The variables of response associated with ovulation were not influenced by BMI or BMI × FI interaction. However, FI influenced length of anovulatory season, as the anovulatory period was 30 d longer (P < 0.05) in the FR group as compared with the NFR group. Independently of treatments, TAF and LFD decreased from the first to the third ultrasonographic ovarian scan (13.2, 10.8 and 4.4 follicles; 3.7, 2.7 and 2.3 mm). Nevertheless, in PER 1 the number of TAF was greater (P < 0.05) in the FR as compared with NFR group and the GBMI group had a larger LFD (P < 0.05) as compared to the LBMI group. It is concluded, that temporal restriction in feed intake could affect the time of cessation and initiation of ovulations during the periods of transition to seasonal anestrus and return to estrous activity, and increase the length of the anovulatory period. In addition, ovarian follicular development during transition into the anovulatory period is differentially influenced by food intake and the status of body energy stores.     

The debate about the biological species concept - a review

The importance of the species concept in biology has led to a continuing debate about the definition of species. This paper summarizes the recent literature in relation to the ‘biological species concept’ (MAYR 1942). Among the general attributes demanded, possible limitations of the universality and applicability of a species definition are discussed. Three different areas of criticism of the biological species concept are considered: 1. The impracticability of the criterion of reproductive isolation. The demand for more practical criteria is rejected, because reproductive isolation is seen as the factor that produces and maintains species as discrete entities in nature. 2. The inapplicability to non-bisexual organisms. A brief survey of modes of uniparental reproduction and their relative importance suggests that obligatory apomicts are of little evolutionary significance. 3. The inapplicability to multidimensional situations. Despite practical difficulties, the biological species concept is held to apply to organisms separated in space. The impossibility to delimit species in time by reproductive isolation is recognized. Out of two ways to divide continuous evolutionary lineages in time, the phylogenetic approach, which considers only speciation events (cladogenesis), is preferred as it is more objective. A list of recently published alternative definitions of species, none of which is found acceptable, is given. It is concluded that the biological species concept needs not be changed or dismissed on the basis of the discussed criticisms.