Seed Ecology (Outline Studies in Ecology)
Since individuals are the target of selection, we think that considering individual variation in eco-physiology can contribute to a more thorough understanding of the evolution of energy-saving strategies in mammals. Image caption: Eastern Chipmunk Tamias striatus.
Large seaweeds and higher plants macrophytes are commonly found in coastal marine habitats where they photosynthesise i.
Primary production underpins aquatic food webs, plays an important role in the global carbon cycle and connects the life from surface ocean layers with the species at the seabed. However, the rate of primary production can greatly vary between species, communities, ecosystems, seas and oceans, simply because species differ in terms of their functional setup and oceans in their environmental settings. Here we investigated the possibility to link functional traits i. We first measured primary production of macrophyte communities and then quantified how large fractions of the total community biomass different traits compose.
By linking community production and trait information we found out that primary production mostly depended on the amount of large epilithic seaweeds of marine origin in the community. Interestingly, we also found that several traits were clustered together meaning that the occurrence of one trait increased the likelihood of another. Our findings suggest that functional traits of macrophytes can be effectively used to monitor primary production.
Furthermore, taxonomically distinct species might possess similar traits meaning that functional aspects of ecosystems can be analysed without extensive taxonomic knowledge. This could result in simplification of the general procedure of production estimations and establish transparent framework how to link community structure with functioning. In many birds males and females show different colours and often males are more colourful than females, a phenomenon called sexual dichromatism. More colourful males are generally favoured by females.
But why would females choose males based on their colours?
One hypothesis states that females choosing colourful males are selecting mates of higher quality. Consequently, sexual selection should lead to the elaboration of colours that honestly signal quality and these should be more sexually dichromatic.
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Certain types of plumage colours, for physiological reasons, may constitute better signals of male quality. Among these are carotenoid-based colours. Carotenoids are yellow to red plant pigments that animals need to ingest in their food and which also play important roles in immune function and health maintenance. These links with food and health, which are particularly strong for red carotenoids, make them good candidates to be sexually selected and dichromatic. Other pigments, such as melanins, are produced within the body and are considered cheaper to produce.
Colours can also be produced by the interaction between light and feather microstructure, known as structural colours, which often have blue, violet or ultraviolet hues. Here we quantify sexual dichromatism for colours produced by different mechanisms including carotenoids in a large sample of Australian birds. By measuring plumage colours on museum specimens and using models of bird colour vision we could estimate how different male and female plumage colours look to birds.
In general, sexual dichromatism was highest when males and females had plumage coloured by different mechanisms of colour production e. This is not surprising, since colours caused by different mechanisms are usually quite different.
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We also found that, as predicted, red carotenoid plumage had higher sexual dichromatism and that species with a higher proportion of their plumage coloured with red carotenoids showed higher levels of sexual dichromatism. However, these correlations did not explain a large amount of variation in sexual dichromatism.
We conclude that knowing the mechanisms behind the different types of colours has only limited utility in predicting which colours should be sexually selected in birds. Plants can exchange information with neighbouring plants and a complex network of herbivores, predators and parasitoids. The language that plants use for such information transfer is, to a great extent, chemical - released into the rhizosphere the soil immediately surrounding the roots or into the air surrounding the plant. We found that plant communication accelerates herbivore movement between host plants while simultaneously reducing herbivory.
This suggests that plant communication can limit herbivore loads by keeping herbivores on the move between host plants. We also demonstrate that volatile chemicals emitted from herbivore-attacked plants are sufficient to explain metabolic responses in, and ecological consequences for, the exposed neighbour plant. Thus, volatile organic compounds emitted by stressed plants provide neighbouring plants with specific information about herbivores in the vicinity.
The attacking herbivores, in turn, respond similarly to directly damaged plants and plants exposed to VOCs from damaged neighbours, as if they were of equivalently poor quality. This study suggests that by enlarging the spatial scale at which induced resistance affects the distribution of plant chemical phenotypes in plant populations, VOC-mediated plant communication alters the movement behaviour and performance of herbivores.
Lara Souza, Katharine L. Biodiversity, often measured as the number of species in a community, can promote services within ecosystems such as sequestration of carbon from the atmosphere.
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Biodiversity within a species, or specifically the number of genotypes within a species, may be just as important in promoting ecosystem services, especially when considering a common species. Solidago altissima , also known as tall goldenrod, is a commonly found plant in abandoned agricultural fields ranging from Florida into northern Canada. Tall goldenrod can make up almost half of the total productivity of old fields and is associated with a large number of insects including herbivores, predators and pollinators.
To explore the role of biodiversity within tall goldenrod, and how the environment may influence biodiversity effects on ecosystem services, we established a field experiment where Solidago genotypes occurred in monocultures vs. Our findings indicate that plant genetic variation, and to some extent plant genotypic diversity, strongly influence carbon sequestration in old fields, and such effects took place regardless of soil nutrient availability.
Image caption: Photo provided by authors. Walter Tschinkel and Joshua King. One of the basic questions of ecology is how and why particular sets of species called communities live together; to what degree does the physical nature of the habitat limit the species present, and to what degree do species' interactions? Solid answers to such questions cannot be derived from the existing species co-occurrence, but must be derived from experiments. The fire ant, Solenopsis invicta , is an exotic, invasive ant found primarily in human-disturbed habitats, and is absent from most undisturbed, native habitat such as the coastal plains pine forests of northern Florida.
However, fire ants quickly colonize soil and vegetation disturbances in these forests and thrive until these revert in time to a less disturbed condition. We previously showed that soil disturbance reduces the native ant populations. Newly-mated, dispersing fire ant queens locate these disturbances while in flight and settle in them preferentially to try to establish new colonies. The question is, do they know what they are doing?
Does settling in such sites improve their chances of success? We set up experimental plots in a Florida pine forest with all combinations of soil tilling, shading and reduction of the native ant community using poison baits. We then planted newly-mated fire ant queens, incipient colonies and small colonies in these plots and followed their survival. By choosing to land in disturbed habitat with its reduced native ant population, newly mated fire ants queens increase their chances of successful colony establishment.
This ant community is thus assembled primarily by queen habitat choice and secondarily by competition. Queens do know what they are doing. Several tilled plots and shade covers are apparent. Carol K. Augspurger, Susan E. Franson, and Katherine C.
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Seeds that disperse further from their parent tree often have a better chance of survival. Also, offspring may arrive in areas of lower seed density and away from the parent tree where fungi and herbivores are less likely to attack them. However, how a parent controls where its offspring are dispersed is unclear. This study provides insights into factors critical in predicting the pattern of seeds that fall around a parent tree. Here, we studied wind-dispersal by 12 Panamanian tree species.
Our results showed that dispersal units with a higher weight to area ratio fell faster in still air. However, this speed of fall did not predict dispersal distance when many dispersal units were released from a 40 m tower in the forest. Likewise, these traits did not explain how far a seed landed after natural dispersal from the parent tree. The pattern of seeds around parent trees of the 12 species differed greatly. We found that taller trees had greater average and maximum seed dispersal distances. Trees dispersing a greater number of seeds also had a greater average dispersal distance.
Generally, the tree variables predicted dispersal distance well, but unaccounted factors about the dispersal unit or the parent tree, or, more likely, variation in wind speeds that seeds experienced after release, were also important. Therefore, tree traits explained dispersal distances of these wind-dispersed species, particularly over long distances where offspring survival is enhanced.
Apparently, a taller tree exposes its seeds to stronger winds, particularly updrafts after they are released, and carries them to farther distances and lower densities, and perhaps to higher light where some offspring may survive. Future studies should focus on wind strengths needed to release the seeds from the tree, as well as wind patterns after release, to improve our understanding of dispersal.
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Image caption: A representative dispersal unit of each of 12 wind-dispersed study species in Panama. The results show that tree height and number of dispersal units, and not how fast the dispersal unit falls, explain the pattern of seeds distributed around the parent tree. Bryophytes mosses are small spore-producing plants that occur in most global ecosystems. Even where they are relatively scarce, such as in semiarid grasslands, bryophytes still may play important roles in various processes such as nutrient cycling, surface water dynamics or vascular plant regeneration.
Human impacts such as projected climate shifts and nutrient deposition are likely to change both the abundances and the ecological role of bryophytes. We simulated two environmental changes, increased springtime rainfall and increased nutrient availability, in a semiarid grassland in California. Both of these changes are already known to make grassland plant communities more productive and more strongly dominated by tall vascular plant species such as exotic annual grasses.
We asked whether bryophytes would show this same competitive suppression of abundance and diversity under enhanced rainfall and nutrients.