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Neanderthal extinction - Wikipedia

We study frequency-dependent seed predation (FDP) in a model of competing annual plant species in a variable environment. The combination of a variable environment and competition leads to the storage-effect coexistence mechanism (SE), which is a leading hypothesis for coexistence of desert annual plants. However, seed predation in such systems demands attention to coexistence mechanisms associated with predation. FDP is one such mechanism, which promotes coexistence by shifting predation to more abundant plant species, facilitating the recovery of species perturbed to low density. When present together, FDP and SE interact, undermining each other's effects. Predation weakens competition, and therefore weakens mechanisms associated with competition: here SE. However, the direct effect of FDP in promoting coexistence can compensate or more than compensate for this weakening of SE. On the other hand, the environmental variation necessary for SE weakens FDP. With high survival of dormant seeds, SE can be strong enough to compensate, or overcompensate, for the decline in FDP, provided predation is not too strong. Although FDP and SE may simultaneously contribute to coexistence, their combined effect is less than the sum of their separate effects, and is often less than the effect of the stronger mechanism when present alone.

N2 - We study frequency-dependent seed predation (FDP) in a model of competing annual plant species in a variable environment. The combination of a variable environment and competition leads to the storage-effect coexistence mechanism (SE), which is a leading hypothesis for coexistence of desert annual plants. However, seed predation in such systems demands attention to coexistence mechanisms associated with predation. FDP is one such mechanism, which promotes coexistence by shifting predation to more abundant plant species, facilitating the recovery of species perturbed to low density. When present together, FDP and SE interact, undermining each other's effects. Predation weakens competition, and therefore weakens mechanisms associated with competition: here SE. However, the direct effect of FDP in promoting coexistence can compensate or more than compensate for this weakening of SE. On the other hand, the environmental variation necessary for SE weakens FDP. With high survival of dormant seeds, SE can be strong enough to compensate, or overcompensate, for the decline in FDP, provided predation is not too strong. Although FDP and SE may simultaneously contribute to coexistence, their combined effect is less than the sum of their separate effects, and is often less than the effect of the stronger mechanism when present alone.

Competitive coexistence of coral-dwelling fishes: the lottery hypothesis revisited

Sturge–Weber Syndrome and Port-Wine Stains Caused …

The negative density-dependent hypothesis focuses mainly on conspecific interactions to explain the coexistence of diverse species in natural communities

Temporal environmental variation is a leading hypothesis for the coexistence of desert annual plants. Environmental variation is hypothesized to cause species-specific patterns of variation in germination, which then generates the storage effect coexistence mechanism. However, it has never been shown how sufficient species differences in germination patterns for multispecies coexistence can arise from a shared fluctuating environment. Here we show that nonlinear germination responses to a single fluctuating physical environmental factor can lead to sufficient differences between species in germination pattern for the storage effect to yield coexistence of multiple species. We derive these nonlinear germination responses from experimental data on the effects of varying soil moisture duration. Although these nonlinearities lead to strong species asymmetries in germination patterns, the relative nonlinearity coexistence mechanism is minor compared with the storage effect. However, these asymmetries mean that the storage effect can be negative for some species, which then only persist in the face of interspecific competition through average fitness advantages. This work shows how a low dimensional physical environment can nevertheless stabilize multispecies coexistence when the species have different nonlinear responses to common conditions, as supported by our experimental data.

N2 - Temporal environmental variation is a leading hypothesis for the coexistence of desert annual plants. Environmental variation is hypothesized to cause species-specific patterns of variation in germination, which then generates the storage effect coexistence mechanism. However, it has never been shown how sufficient species differences in germination patterns for multispecies coexistence can arise from a shared fluctuating environment. Here we show that nonlinear germination responses to a single fluctuating physical environmental factor can lead to sufficient differences between species in germination pattern for the storage effect to yield coexistence of multiple species. We derive these nonlinear germination responses from experimental data on the effects of varying soil moisture duration. Although these nonlinearities lead to strong species asymmetries in germination patterns, the relative nonlinearity coexistence mechanism is minor compared with the storage effect. However, these asymmetries mean that the storage effect can be negative for some species, which then only persist in the face of interspecific competition through average fitness advantages. This work shows how a low dimensional physical environment can nevertheless stabilize multispecies coexistence when the species have different nonlinear responses to common conditions, as supported by our experimental data.

Metaphysics for Dummies - F oo l Q uest. com

AB - Temporal environmental variation is a leading hypothesis for the coexistence of desert annual plants. Environmental variation is hypothesized to cause species-specific patterns of variation in germination, which then generates the storage effect coexistence mechanism. However, it has never been shown how sufficient species differences in germination patterns for multispecies coexistence can arise from a shared fluctuating environment. Here we show that nonlinear germination responses to a single fluctuating physical environmental factor can lead to sufficient differences between species in germination pattern for the storage effect to yield coexistence of multiple species. We derive these nonlinear germination responses from experimental data on the effects of varying soil moisture duration. Although these nonlinearities lead to strong species asymmetries in germination patterns, the relative nonlinearity coexistence mechanism is minor compared with the storage effect. However, these asymmetries mean that the storage effect can be negative for some species, which then only persist in the face of interspecific competition through average fitness advantages. This work shows how a low dimensional physical environment can nevertheless stabilize multispecies coexistence when the species have different nonlinear responses to common conditions, as supported by our experimental data.

Munday, Philip L. (2004) Competitive coexistence of coral-dwelling fishes: the lottery hypothesis revisited. Ecology, 85 (3). pp. 623-628.

Summary:
Incomplete specific recognition can lead to the occurrence of reproductive interference (RI) - reproductive interactions between two species resulting in fitness loss for at least one of them. RI can play an important role in the coexistence of species, being especially important in the fate of introduced exotic species and in pest management.Tetranychus urticae and Tetranychus evansi are two closely related haplodiploid spider mite species that often coexist in solenaceous crops. Incomplete specific recognition occurs among these species: heterospecific matings were observed, although no hybrid progeny has been found. We tested two possible RI mechanisms: (1) the effect of mating with heterospecifics on virgin (haploid) offspring and (2), the consequences of heterospecific crosses for the offspring of females that have or will mate with conspecifics. Behavioural assays showed that (1) only T. urticae females and T. evansi males prefer to mate with conspecifics; (2) regarding latency to copulation individuals behave as virgins after mating heterospecifically, (3) T. urticae females copulate for a shorter period with heterospecifics than with conspecifcs. Results for fecundity and sex-ratio revealed that (1) for both species, fecundity of females mated with heterospecifics are similar to that of virgins - heterospecific crosses do not affect egg viability; (2) T. evansi females that mate with both conspecific and heterospecific males had higher fecundity than females that mated with a conspecific male only; this was not observed in T. urticae. (3) T. urticae females that mate with a heterospecific male after a conspecific mating had a lower percentage of female offspring. The results obtained point to the occurrence of asymmetric RI, in which T. evansi females benefits from mating with heterospecifics, whereas T. urticae pay a cost of such matings. These results may affect the coexistence of these species, a hypothesis requiring further testing.

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International Zoo Educators Association


Paroxysmal hemicrania: Clinical features and diagnosis

AB - We study frequency-dependent seed predation (FDP) in a model of competing annual plant species in a variable environment. The combination of a variable environment and competition leads to the storage-effect coexistence mechanism (SE), which is a leading hypothesis for coexistence of desert annual plants. However, seed predation in such systems demands attention to coexistence mechanisms associated with predation. FDP is one such mechanism, which promotes coexistence by shifting predation to more abundant plant species, facilitating the recovery of species perturbed to low density. When present together, FDP and SE interact, undermining each other's effects. Predation weakens competition, and therefore weakens mechanisms associated with competition: here SE. However, the direct effect of FDP in promoting coexistence can compensate or more than compensate for this weakening of SE. On the other hand, the environmental variation necessary for SE weakens FDP. With high survival of dormant seeds, SE can be strong enough to compensate, or overcompensate, for the decline in FDP, provided predation is not too strong. Although FDP and SE may simultaneously contribute to coexistence, their combined effect is less than the sum of their separate effects, and is often less than the effect of the stronger mechanism when present alone.

Philosophy of Religion | Internet Encyclopedia of Philosophy

Incomplete specific recognition can lead to the occurrence of reproductive interference (RI) - reproductive interactions between two species resulting in fitness loss for at least one of them. RI can play an important role in the coexistence of species, being especially important in the fate of introduced exotic species and in pest management.Tetranychus urticae and Tetranychus evansi are two closely related haplodiploid spider mite species that often coexist in solenaceous crops. Incomplete specific recognition occurs among these species: heterospecific matings were observed, although no hybrid progeny has been found. We tested two possible RI mechanisms: (1) the effect of mating with heterospecifics on virgin (haploid) offspring and (2), the consequences of heterospecific crosses for the offspring of females that have or will mate with conspecifics. Behavioural assays showed that (1) only T. urticae females and T. evansi males prefer to mate with conspecifics; (2) regarding latency to copulation individuals behave as virgins after mating heterospecifically, (3) T. urticae females copulate for a shorter period with heterospecifics than with conspecifcs. Results for fecundity and sex-ratio revealed that (1) for both species, fecundity of females mated with heterospecifics are similar to that of virgins - heterospecific crosses do not affect egg viability; (2) T. evansi females that mate with both conspecific and heterospecific males had higher fecundity than females that mated with a conspecific male only; this was not observed in T. urticae. (3) T. urticae females that mate with a heterospecific male after a conspecific mating had a lower percentage of female offspring. The results obtained point to the occurrence of asymmetric RI, in which T. evansi females benefits from mating with heterospecifics, whereas T. urticae pay a cost of such matings. These results may affect the coexistence of these species, a hypothesis requiring further testing.

Scientific Papers and Articles - The Shroud of Turin …

The association between species richness and ecosystem energy availability is one of the major geographic trends in biodiversity. It is often explained in terms of energetic constraints, such that coexistence among competing species is limited in low productivity environments. However, it has proven challenging to reject alternative views, including the null hypothesis that species richness has simply had more time to accumulate in productive regions, and thus the role of energetic constraints in limiting coexistence remains largely unknown. We use the phylogenetic relationships and geographic ranges of sister species (pairs of lineages who are each other’s closest extant relatives) to examine the association between energy availability and coexistence across an entire vertebrate class (Aves). We show that the incidence of coexistence among sister species increases with overall species richness and is elevated in more productive ecosystems, even when accounting for differences in the evolutionary time available for coexistence to occur. Our results indicate that energy availability promotes species coexistence in closely related lineages, providing a key step toward a more mechanistic understanding of the productivity–richness relationship underlying global gradients in biodiversity.

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