Congeneric Individuals Research Articles

Plant size and neighbourhood characteristics influence survival and growth in a restored ex‐agricultural ecosystem

Abstract Restoring woody vegetation on degraded agricultural land is a widespread and common ecological restoration practice. However, highly variable plant survival and growth limit outcomes for many projects. Inconsistent reporting and monitoring of projects mean that an assessment of the relative importance of community‐assembly processes is limited, particularly over longer timescales. We use 7 years of monitoring data of nearly 2000 native trees and shrubs in a restoration project on ex‐agricultural land in south‐western Australia to test the potential effects of facilitation or competition from neighbouring plants, as well as look for patterns in their interaction with the attributes of individuals and species traits. Overall, plant size was the strongest single predictor of survival and incremental growth. Individual plants in neighbourhoods with higher inter‐generic basal area were more likely to survive, with this effect strongest in smaller individuals. When plants were larger, they were less likely to grow when in neighbourhoods with high intra‐generic basal area. Taller‐growing plants (higher species maximum height) were more likely to survive when individuals were small (basal area of 1–10 cm2), compared with shorter growing plants. Growth was also more likely in taller‐growing plants, and this relationship increased with the size of the individual. Recruitment was very low, with just 148 new recruits recorded across the 42 plots over 7 years. Maximizing the growth of plants in restorations in the early stages may promote survival and growth in the longer term. We also demonstrate that increased levels of inter‐generic neighbouring plants may improve individual plant survival in the restoration of ex‐agricultural land. As a result, we suggest tailoring direct‐seeding methods to minimize clustering of congeneric individuals. We also highlight the need to find means of promoting recruitment for the long‐term sustainability of restoration efforts.

Modelling the effects of the repellent scent marks of pollinators on their foraging efficiency and the plant-pollinator community.

Pollinator insects forage in complex and unpredictable resource landscapes, often using social information from congeneric individuals to acquire knowledge about their environment. It has long been recognized that this process allows them to exploit floral resources more efficiently and thus increase individual fitness. However, by creating correlations between the behaviors of pollinators within a population, this could also indirectly influence the entire plant-pollinator community. One type of social information used by pollinators is the scent mark left on the corolla of flowers by previous visitors, which can be used as a cue to avoid recently depleted resources. We developed a spatially explicit agent-based model to examine the effects, at both individual and community levels, of pollinators using these scent marks. The model simulates a population of pollinators foraging on flowers in a continuous 2D space in which we can vary the density of pollinators. We showed that the use of scent marks as a source of information significantly increased the foraging efficiency of pollinators except when competition between pollinators was very low. At the community level, this also resulted in a marked homogenization between floral resources within the landscape: in the absence of scent marks, the coefficient of variation of the remaining nectar quantity per flower strongly increased with greater pollinator competition, but it remained low at all levels of competition when scent marks were used by the pollinators. Finally, the use of scent marks markedly decreased the number of pollinator flower visits, especially at high levels of pollinator competition, which can potentially reduce the pollination service.

Feeding habits and trophic interactions of four sympatric hammerhead shark species reveal trophic niche partitioning

Knowledge of the ecological roles of species within food webs and how their trophic interactions affect food web structure is critical to model management and conservation scenarios for species that are suffering high levels of anthropogenic pressure, such as hammerhead sharks. In this paper, we analyze the diet and trophic relationships of 4 sympatric hammerhead shark species using a combination of stomach content and stable isotope analyses. These species showed trophic similarities by sex and trophic dissimilarities by maturity stage. We found that the trophic niche of hammerhead species tends to be more similar within species than among them. This suggests that competitive interactions are more likely to occur between conspecifics than between congeneric individuals and highlights the potential different roles that these species can play within the food web structure. The intermediate to high trophic positions observed inSphyrna corona,S.media,S.tiburoandS.lewinijuveniles indicate mesopredator roles, whereasS. lewinisubadults could be considered top predators. Our findings revealed multiple trophic interactions between hammerhead sharks and prey from different trophic levels, which could be critical for the structure and function of marine food webs.

New records of two Lutjanus species (Teleostei: Perciformes: Lutjanidae) with re-description of six lutjanids from Saint Martin’s Island of the Bay of Bengal, Bangladesh

Investigations on Snapper fish of the genus Lutjanus were conducted from October 2015 to April 2016 in the coral ecosystem of St. Martin’s Island, Bangladesh. Twenty one individuals of 8 species of Lutjanus were collected from local fishermen. Both morphological characters and DNA barcoding approach by mitochondrial cytochrome oxidase I subunit (COI) were used to confirm the identification of all species. Present study recorded the first national occurrence of two reef associated Lutjanus species (L. xanthopinnis and L. indicus). In addition six species (L. rivulatus, L. lutjanus, L. vitta, L. lemniscatus, L. fulviflamma and L. johnii) were re-described. Distinct morphological differentiation were found between more closely related species L. xanthopinnis, L. vitta and L. lutjanus. Three different appearances of L. johnii, two different appearances of L. rivulatus and L. lemniscatus were confirmed as same species. Phylogenetic analysis showed monophylotic clade for conspecific individuals and paraphyletic clade for congeneric individuals. Average genetic divergence for intraspecific level was 1.5% and 12.5% for interspecific level. Current study increased the number of Lutjanus species in Bangladesh from 15 to 17 and extended the distribution range of those new recorded species in northeastern part of the Bay of Bengal.
 Bangladesh J. Zool. 46(2): 239-253, 2018

Offspring discrimination by female parents of the matriphagous spider Cheiracanthium japonicum (Araneae: Eutichuridae)

ABSTRACTThe ability of females of the matriphagous spider Cheiracanthium japonicum to discern their own offspring was examined based on a comparison of her maternal care for her own eggs and spiderlings with other conspecific females as well as those of other congeneric species. Cheiracanthium japonicum females did not discern their own nest from those of conspecific and congeneric individuals. In addition, the female did not distinguish her own egg sac from those of other conspecific or congeneric individuals. On the other hand, the female clearly discriminated between her own spiderlings and those of other congeneric species only if the congeneric spiderlings were introduced into the breeding nest. Consequently, the female will allow conspecific spiderlings to predate her (i.e. cannibalism). However, it is hardly expected that spiderlings of a certain female would eat another female in the field, as the reproductive period is quite short and synchronised in a population. Considering that the female can only recognise spiderlings of other species, the recognition ability of C. japonicum females will be evolved only to work as a protection against intruders of other species into the breeding nest.

A molecular analysis of selected marine fishes from the southwest coast of India for species delineation

In this study, mitochondrial genes 16S and cytochrome C oxidase I (COI) were used as taxonomic markers for the molecular analysis of selected fishes from the southwest coastal waters of India, viz., Sillago sihama (Forsskal, 1775), Mene maculata (Bloch & Schneider, 1801), Seriolina nigrofasciata (Ruppell, 1829), and Minous dempsterae (Eschmeyer, Hallacher & Rama-Rao, 1979). Both the gene fragments showed diagnostic differences and divergence within each taxon. The mean nucleotide diversity (Pi) among all the species was estimated as 0.083. The average transition and transversion ratio was 1.63. The average K2P distance of species within genera was estimated as 13.71 %, whereas it was 20.22 % among species within families. The variation was more among the species within families than among the congeneric individuals. The study on the phylogenetic relationships among the species revealed distinct clusters in concurrence with the taxonomic status of the species. The study also suggests that the mtDNA 16S (rRNA) and COI genes can be used as barcodes for the identification of fish species based on sequence information.

Hybridization betweenMauremys japonicaandMauremys reevesiiInferred by Nuclear and Mitochondrial DNA Analyses

The Japanese Pond Turtle, Mauremys japonica, and the Reeves' Pond Turtle, Mauremys reevesii, are common aquatic geoemydid species in Japan. The former is endemic to Japan, whereas the latter is distributed widely throughout East Asia, China, Korea, Taiwan, and Japan. Although the Japanese populations of M. reevesii were generally considered to be indigenous, it was suggested recently that Japanese M. reevesii is derived from multiple artificial introductions from elsewhere in Asia. Putative hybrid individuals, with intermediate morphological characters, have been observed in the wild. Furthermore, captive congeneric individuals have produced viable offspring that attained sexual maturity. To clarify the extent of hybridization between these species, we examined nuclear DNA and mitochondrial DNA genetic markers of putative hybrids collected in the field. We found that most of the animals assayed had nuclear DNA derived from both species. In addition, several individuals originated from hybrid mothers implying that hybridization is indeed occurring in the wild and that female hybrids are fertile and reproduce. Our results indicate an ongoing process of introgression of introduced M. reevesii alleles into the gene pool of native populations of M. japonica.

Morphologic Variation in Aegla Leach (Decapoda: Reptantia: Aeglidae) from Central-Southern Chile: Interspecific Differences, Sexual Dimorphism, and Spatial Segregation

Abstract How do certain characteristics of organisms, such as sex or species, and certain ecological factors, such as interaction with congeneric individuals, influence the variability of body architecture in an environmental setting over a small spatial scale? Using geometric morphometrics we performed a morphological comparison of the dorsal surface of the carapace of a congeneric guild formed by Aegla araucaniensis, A. denticulata denticulata, and A. abtao. Additionally, we evaluated whether the segregation of microhabitat by congeneric interactions generates variations in the shape of the cephalothorax in A. araucaniensis, comparing a population belonging to the congeneric guild with a close population without congeneric interactions. Changes in cephalothoracic shape are regulated primarily by intrinsic factors, such as the differences between species and sex of individuals. In addition, the congeneric interactions do not affect the expression of the carapace shape in either of the populations of A. a...

Cryptic interference competition in swans foraging on cryptic prey

Interference can be defined as the reduction of intake rate caused by the presence of congeneric individuals. However, surrounding congeneric individuals may also accelerate food depletion. Therefore, it is difficult to quantify interference (contest) and exploitative (scramble) competition separately, particularly in the field. In an individual-based model, where food was immediately replenished in patches after a foraging bout, we isolated the effect of interference competition. In this way, we investigated how interference shapes the intake rates of flocking Bewick’s swans, Cygnus bewickii, consuming tubers of fennel pondweed, Potamogeton pectinatus. The model predicted that intake rate declines with increasing swan density, and that the rate of decline is greater in subordinate birds than in dominant birds. Subordinate birds suffered a large reduction in intake rate at high densities because they spent a large proportion of the time avoiding more dominant individuals. A major decline in intake rate of subordinates occurred close to the maximum swan densities observed in the field. We expected subordinates to leave high-density flocks and look for another foraging location: interference competition seemed to regulate the maximum swan flock density in the field. Hence, the mean population intake rate at realized densities was only slightly lower than in the absence of interference. As interference occurred mainly as avoidance behaviour, which is difficult to observe in the field, it might commonly remain cryptic for the observer. Our results may explain other field studies where interference competition seemed to be of lesser importance.

Chemical Defence in Cephalaspidean Gastropods: Origin, Anatomical Location and Ecological Roles

Within the opisthobranchs, the cephalaspideans are traditionally considered a transitional group between typical testacean prosobranchs and shell-less opisthobranchs. The cephalaspidean anatomy, including the presence of a cephalic shield, is related to burrowing through soft sediment. Recent studies have shown that some herbivorous and carnivorous cephalaspideans contain secondary metabolites. The micro-herbivorous bubble snails of the Bullidae and Haminoeidae families are known to have secondary metabolites which have different ecological roles. The polypropionates isolated from Bulla gouldiana and B. striata were deterrent to fishes while the secondary metabolites of Haminoea callidegenita, H. fusari, H. hydatis, H. navicula, H. orbignyana and H. orteai were alarm pheromones employed during cross copulation. In Bulla gouldiana and B. striata, the defensive secretion was located mainly in a white gland along the margin of the mantle. In Haminoea species, alarm pheromones were located in external parts (cephalic shield, parapodial lobes and posterior pallial lobe). The carnivorous cephalaspideans Navanax inermis and Philinopsis depicta employ chemotaxis to follow the slime trail of their prey, which include other cephalaspideans or even congeneric individuals. N. inermis and P. depicta sequester alarm pheromones and allomones from their cephalaspidean prey, which are ejected when N. inermis and P. depicta are disturbed. The specific metabolic patterns of Mediterranean cephalaspideans suggest that these patterns can be used as chemotaxonomic markers. We propose the use of a single Thin Layer Chromatography to differentiate among Mediterranean Haminoea species.

Alarm responses in the crayfishOrconectes virilis andOrconectes propinquus

Individuals of two species of crayfish (Orconectes virilis andO. propinquus) were tested in the laboratory for responses to chemicals released from physically damaged conspecifics. Individuals ofO. propinquus did not show an alarm response to crushed conspecifics. Individuals ofO. virilis responded to a water-borne substance released from crushed conspecifics by assuming an intermediate posture and ceasing movement. Similar alarm responses were shown by individuals ofO. virilis to crushed congeneric individuals (O. propinquus), and these responses were not eliminated by either freeze-thawing the crayfish used to prepare the signal or by treating freshly crushed crayfish with the enzyme trypsin. Individuals ofO. virilis showed strong feeding responses to solutions prepared from frozen fish flesh but showed a mixture of alarm and feeding responses to freshly killed fish. These results indicate that the alarm substance used byO. virilis is widespread.