Reproductive Success Of Native Species Research Articles

An invasive alien Proteaceae lures some, but not all nectar-feeding bird pollinators away from native Proteaceae in South African fynbos.

Invasive alien plants often influence pollinator visitation to native plants when sharing pollinator guilds. It is of conservation concern when the invasive alien plant is characterized by floral resources that attract pollinators, thereby reducing the reproductive success of native species. This is well studied for insects, but whether the same is true for bird pollinators is largely unknown. We address this by considering the impact of an invasive alien plant (Banksia speciosa) on visitation rates of nectar-feeding bird pollinators to native Protea compacta in the Cape Floristic Region of South Africa. We determined bird pollinator visitation rate to B. speciosa and P. compacta over 21h of observation at three sites. We also quantified how visitation rate influenced reproductive success of both study species through different breeding experiments. Sugarbird visitation to P. compacta was significantly lower in the presence of B. speciosa, while there was no effect for sunbirds as they mostly avoided B. speciosa. Protea compacta had higher nectar volumes and sucrose per flower than B. speciosa. Sucrose per hectare was higher in all P. compacta plots compared to B. speciosa. Neither study species is pollen limited and they are self-compatible to some extent. But pollinator visitation enhanced seed production in both species. We show here that the invasive alien B. speciosa flowers attract sugarbirds - but not sunbirds - away from native P. compacta. The long-term effect of reduced pollinator visitation may reduce the fitness of P. compacta, but the long-term demographic impact is unknown and would require further study.

Invasion status and phylogenetic relatedness predict cost of heterospecific pollen receipt: implications for native biodiversity decline

SummaryUnderstanding the mechanisms by which invasive species affect native plants is a central challenge. Invasive plants have been shown to reduce pollinator visitation to natives and increase pollen quantity limitation. However, visitation and conspecific pollen delivery are the only two components of the pollination process; post‐pollination interactions on the stigma (heterospecific pollen [HP] receipt) could intensify pre‐pollination responses to invasion.Here, we used meta‐analysis to test the hypotheses that invasive plants are more detrimental asHPdonors than natives ones and thatHPdonors that are closely related to the recipients have stronger effects on fruit and seed production compared to distantly related ones.InvasiveHPdonors reduced fruit and seed production of recipients to a greater degree than native ones, and this was more intense forHPdonors closely related to natives. Related donors were more detrimental overall.Synthesis. These results suggest that the total effect of invasive plants on native plant reproductive success could be greater than what is inferred from visitation and conspecific pollen transfer alone. Furthermore, these results indicate that invasive species can reduce reproductive success of native species even if pollinator visitation rates remain unaltered. Thus, we highlight the need to evaluate pre‐ and post‐pollination processes in order to fully understand the potential effects of invasive species on the reproductive success and maintenance of native plant populations.

Reproductive success of Cabralea canjerana (Meliaceae) in Atlantic forest fragments, Brazil

In Brazil, the Atlantic forest remnants have high biological diversity and a high level of endemism, but very little is known about the reproductive success of native species. <em>Cabralea canjerana</em> is a common tree in the Montane Atlantic forest, and its reproduction is highly dependent on pollinators. In order to contribute with the particular knowledge on this species, we collected data in three fragmented and three continuous forest sites, where the effects of fragmentation on both mutualistic (pollination) and antagonistic (seed predation) interactions were analysed. We determined fruit production and weight of 25 trees per site. The number of seeds and the percentage of predated and aborted seeds were also accessed for seven fruits of 10 trees per site. Pollinator visitation frequencies to flowers were recorded in two forest fragments and in two sites of the continuous forest. Our data showed<em> </em>that plants of <em>C. canjerana</em> produced more fruits (z-value=-8.24; p<0.0001) and seeds per fruit (z-value=-6.58; p=0.002) in the continuous than in the fragmented sites. This was likely due to differences in pollination, because the number of pollinator visits was higher in the continuous forest than in the fragments. Seed abortion (z-value=4.08, p<0.001) and predation (z-value=3.72, p=0.0002), on the other hand, were higher in the fragmented than in the continuous sites. Then, mutualistic and antagonistic interactions were affected by fragmentation, decreasing the reproductive success of the study tree. This study was the first to show a decrease in the reproductive output in forest fragments in an Atlantic forest tree species. This decrease may threaten the population structure and viability of <em>C. canjerana</em> in forest fragments.

An Invasive Plant Species Decreases Native Plant Reproductive Success

Invasive plants may have negative, positive, or neutral effects on the reproductive success of native plant species. In this study, I investigated the impact of the rhizomatous invasive species Securigera varia (Fabaceae; crown vetch; synonym: Coronilla varia) on the reproductive success of the native prairie species Tradescantia ohiensis (Commelinaceae; Ohio spiderwort). In particular, I examined how T. ohiensis plant height, fruit set, seed set, and stigma pollen load differed inside or at the edge of crown vetch patches and within native prairie not invaded by crown vetch. A significant reduction in reproductive success and pollen deposition was detected among T. ohiensis plants in the interior of a crown vetch patch compared to those at the edge of a crown vetch patch. These, in turn, had lower reproductive success and pollen deposition than plants in the native prairie areas. Also, T. ohiensis plants were taller inside crown vetch patches. The results of this study suggest that rhizomatous invasive species such as Securigera varia can have direct and indirect impacts on the reproductive success of native species.

Acoustic invasion: How invasive species can impact native species acoustic niche?

The effects of invasive species on native taxa due to direct predation, food, and space competition, and disease transmission are well documented. However, the effects of acoustic invaders on animal communication have not been explored. We simulated an invasion of the acoustic niche by exposing calling native male white-banded tree frogs (Hypsiboas albomarginatus, harmonics at 60–1430 Hz and 2720–2780 Hz or 2280–2850 Hz) to recorded calls of the invasive American bullfrog (Lithobates catesbeianus, frequencies from 90 to >4000 Hz) at a non-invaded site in the Brazilian Atlantic Forest. In response, tree frogs immediately shifted calls to significantly higher frequencies. In the post-stimulus period, they continued to use higher frequencies and also decreased signal duration. Tree frogs did not change calling rate or inter-call interval. Acoustic signals are the primary basis of mate selection in many anurans, and such changes could negatively affect the reproductive success of native species. The effects of bullfrog vocalizations on acoustic communities are expected to be especially severe due to their broad frequency band, which masks the calls of multiple species simultaneously. These results show that invasive species could affect native species by interfering in their acoustic niche.

Surviving in sprawling suburbs: Suburban environments represent high quality breeding habitat for a widespread shorebird

Throughout the world, urban sprawl converts agricultural land to urban environments, however, little is known of the influence of such landscape change on the reproductive success of native species. We predicted that reproductive success would be suppressed by urban sprawl through habitat degradation and indirectly through compromised quality of parental care from human disturbance. We studied the masked lapwing, Vanellus miles, a common ground-nesting species that occurs in both agricultural and suburban landscapes. Contrary to our predictions, parents in suburban environments invested more in defence of eggs (aggression and distraction) yet suburban female lapwings were in better condition (7% heavier) and laid 2% longer eggs than agricultural female lapwings, suggesting greater access to food resources in suburban than agricultural environments. Lapwings had higher hatching success in suburban compared with agricultural environments, leading to greater reproductive success; a similar rate of chick mortality was evident between environments. The conversion of land from agriculture to suburbia results in species which are winners and losers, some of which (e.g., for species such as the ground-nesting lapwing) are difficult to predict a priori. Despite an overall trend of decreasing avian diversity with increasing urbanisation world-wide, suburban environments have the capacity to act as high quality breeding habitat for species such as the masked lapwing, although such species may be the exception rather than the rule.

Biological invasions and the acoustic niche: the effect of bullfrog calls on the acoustic signals of white-banded tree frogs

Invasive species are known to affect native species in a variety of ways, but the effect of acoustic invaders has not been examined previously. We simulated an invasion of the acoustic niche by exposing calling native male white-banded tree frogs (Hypsiboas albomarginatus) to recorded invasive American bullfrog (Lithobates catesbeianus) calls. In response, tree frogs immediately shifted calls to significantly higher frequencies. In the post-stimulus period, they continued to use higher frequencies while also decreasing signal duration. Acoustic signals are the primary basis of mate selection in many anurans, suggesting that such changes could negatively affect the reproductive success of native species. The effects of bullfrog vocalizations on acoustic communities are expected to be especially severe due to their broad frequency band, which masks the calls of multiple species simultaneously.

Interspecific pollinator movements reduce pollen deposition and seed production inMimulus ringens(Phrymaceae)

Movement of pollinators between coflowering plant species may influence conspecific pollen deposition and seed set. Interspecific pollinator movements between native and showy invasive plants may be particularly detrimental to the pollination and reproductive success of native species. We explored the effects of invasive Lythrum salicaria on the reproductive success of Mimulus ringens, a wetland plant native to eastern North America. Pollinator flights between these species significantly reduced the amount of conspecific pollen deposited on Mimulus stigmas and the number of seeds in Mimulus fruits, suggesting that pollen loss is an important mechanism of competition for pollination. Although pollen loss is often attributed to pollen wastage on heterospecific floral structures, our novel findings suggest that grooming by bees as they forage on a competitor may also significantly reduce outcross pollen export and seed set in Mimulus ringens.