Reid's paradox of rapid plant migration

Last updated

Reid's Paradox of Rapid Plant Migration or Reid's Paradox, describes the observation from the paleoecological record that plant ranges shifted northward, after the last glacial maximum, at a faster rate than the seed dispersal rates commonly occur. [1] [2] Rare long-distance seed dispersal events have been hypothesized to explain these fast migration rates, but the dispersal vector(s) are still unknown. The plant species' geographic range expansion rates are compared to the actualistic rates of seed dispersal using mathematical models, and are graphically visualized using dispersal kernels. [2] [3] These observations made in the paleontological record, which inspired Reid's Paradox, are from fossilized remains of plant parts, including needles, leaves, pollen, and seeds, that can be used to identify past shifts in plant species' ranges.

Contents

Reid's Paradox is named after Clement Reid, a paleobotanist, who made the principle observations from the paleobotanical record in Europe in 1899. His comparison of oak tree seed dispersal rates, and the observed range of oak trees from the fossil record, did not concur. Reid hypothesized that diffusion was not a possible explanation for the observed paradox, and supplemented his hypothesis by noting that birds were the likely cause of long range seed dispersal. [1] Reid's Paradox has been subsequently documented across Europe and North America. [2] [3] [4]

Dispersal kernels

Dispersal kernels are statistical models that represent the probability of seed dispersal from the source tree. Realistic biological data is required to complete the models. These data are used to accurately fill in variables such as seed number, seed size, and reproductive age. [3] Depending on the plant species, the variables in the equation will change. In the years since Reid hypothesized the methods for seed dispersal, the models have gained more complex elements which attempt to resolve Reid's Paradox. [2]

Dispersal kernels representing seed frequencies at increasing distances from the parent tree Seed Dispersal Kernels.png
Dispersal kernels representing seed frequencies at increasing distances from the parent tree

The dispersal of seeds from a parent tree are initially occurs as a normal distribution, as predicted by a standard diffusion equation. However, biological phenomenon complicate the diffusion equation by adding biotic vectors of dispersal such as blue jays and eastern grey squirrels, species which possess caching behaviors, and abiotic agents of dispersal such as high velocity wind storms. [2] These additional vectors of seed dispersal make the dispersal kernels have a "fat-tail", or a large kurtosis. This means that the probability of a long-range dispersal event is higher than that of the standard diffusion dispersal kernel. [2] [3] [5] In order to resolve Reid's Paradox, the vector(s) of seed-dispersal, which give the dispersal kernel a fat-tail, must be identified.

Possible explanations for Reid's Paradox

Animal dispersal

Long distance seed-dispersal events due to animal-seed interactions (such as caching or endozoochorous dispersal) would fatten the tail of the dispersal kernels. To fully explain Reid's Paradox, these rare animal induced seed-dispersal events must have been more important during migration events than recognized or recorded currently. [1] [3]

Cryptic refugia

Small populations of plants may have grown closer to the ice sheets in microhabitats that possessed the habitat characteristics needed for growth and reproduction. This would minimize the actual post-glacial dispersal distance. Such hypothetical populations would not be abundant enough to leave fossil evidence, so have escaped detection. In North America, there is some genetic evidence of cryptic northern refugia for sugar maple and American beech. [6] [4]

Related Research Articles

<span class="mw-page-title-main">Herbivore</span> Organism that eats mostly or exclusively plant material

A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material.

Phylogeography is the study of the historical processes that may be responsible for the past to present geographic distributions of genealogical lineages. This is accomplished by considering the geographic distribution of individuals in light of genetics, particularly population genetics.

<i>Araucaria bidwillii</i> Species of tree in the family Araucariaceae

Araucaria bidwillii, commonly known as the bunya pine, bunya-bunya, or sometimes the monkey puzzle tree, is a large evergreen coniferous tree in the family Araucariaceae which is endemic to Australia. Its natural range is southeast Queensland with two very small, disjunct populations in northeast Queensland's World Heritage listed Wet Tropics. The southern population was, and is, of very high cultural significance to the indigenous tribes of the region. There are many planted specimens on the Atherton Tableland, in New South Wales, and around the Perth metropolitan area, and it has also been widely planted in other parts of the world. They are very tall trees – the tallest living individual is in Bunya Mountains National Park and was reported by Robert Van Pelt in January 2003 to be 51.5 m (169 ft) in height.

<span class="mw-page-title-main">Biological dispersal</span> Movement of individuals from their birth site to a breeding site

Biological dispersal refers to both the movement of individuals from their birth site to their breeding site, as well as the movement from one breeding site to another . Dispersal is also used to describe the movement of propagules such as seeds and spores. Technically, dispersal is defined as any movement that has the potential to lead to gene flow. The act of dispersal involves three phases: departure, transfer, settlement and there are different fitness costs and benefits associated with each of these phases. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population genetics, and species distribution. Understanding dispersal and the consequences both for evolutionary strategies at a species level, and for processes at an ecosystem level, requires understanding on the type of dispersal, the dispersal range of a given species, and the dispersal mechanisms involved.

<span class="mw-page-title-main">Seed dispersal</span> Movement or transport of seeds away from the parent plant

In spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vectors, such as the wind, and living (biotic) vectors such as birds. Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time. The patterns of seed dispersal are determined in large part by the dispersal mechanism and this has important implications for the demographic and genetic structure of plant populations, as well as migration patterns and species interactions. There are five main modes of seed dispersal: gravity, wind, ballistic, water, and by animals. Some plants are serotinous and only disperse their seeds in response to an environmental stimulus. These modes are typically inferred based on adaptations, such as wings or fleshy fruit. However, this simplified view may ignore complexity in dispersal. Plants can disperse via modes without possessing the typical associated adaptations and plant traits may be multifunctional.

<span class="mw-page-title-main">Holarctic realm</span> Biogeographic realm

The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical region, and Alfred Wallace's Palearctic zoogeographical region.

<span class="mw-page-title-main">Seed predation</span> Feeding on seeds as a main or exclusive food source

Seed predation, often referred to as granivory, is a type of plant-animal interaction in which granivores feed on the seeds of plants as a main or exclusive food source, in many cases leaving the seeds damaged and not viable. Granivores are found across many families of vertebrates as well as invertebrates ; thus, seed predation occurs in virtually all terrestrial ecosystems. Seed predation is commonly divided into two distinctive temporal categories, pre-dispersal and post-dispersal predation, which affect the fitness of the parental plant and the dispersed offspring, respectively. Mitigating pre- and post-dispersal predation may involve different strategies. To counter seed predation, plants have evolved both physical defenses and chemical defenses. However, as plants have evolved seed defenses, seed predators have adapted to plant defenses. Thus, many interesting examples of coevolution arise from this dynamic relationship.

In mathematics, an integrodifference equation is a recurrence relation on a function space, of the following form:

<span class="mw-page-title-main">Dispersal vector</span>

A dispersal vector is an agent of biological dispersal that moves a dispersal unit, or organism, away from its birth population to another location or population in which the individual will reproduce. These dispersal units can range from pollen to seeds to fungi to entire organisms.

Forest migration or assisted migration is the movement of large seed plant dominated communities in geographical space over time.

Monodominance is an ecological condition in which more than 60% of the tree canopy comprises a single species of tree. Monodominant forests are quite common under conditions of extra-tropical climate types. Although monodominance is studied across different regions, most research focuses on the many prominent species in tropical forests. Connel and Lowman, originally called it single-dominance. Conventional explanations of biodiversity in tropical forests in the decades prior to Connel and Lowman's work either ignored monodominance entirely or predicted that it would not exist.

Picea critchfieldii is an extinct species of spruce tree formerly present on the landscape of North America, where it was once widely distributed throughout the southeastern United States. Plant macrofossil evidence reveals that this tree became extinct during the Late Quaternary period of Earth's history. At present, this is the only documented plant extinction from this geologic era. Hypotheses as to what specifically drove the extinction remain unresolved, but rapid and widespread climatic changes coincided with Picea critchfieldii's decline and ultimate extinction.

Cross-species transmission (CST), also called interspecies transmission, host jump, or spillover, is the transmission of an infectious pathogen, such as a virus, between hosts belonging to different species. Once introduced into an individual of a new host species, the pathogen may cause disease for the new host and/or acquire the ability to infect other individuals of the same species, allowing it to spread through the new host population. The phenomenon is most commonly studied in virology, but cross-species transmission may also occur with bacterial pathogens or other types of microorganisms.

A glacial refugium is a geographic region which made possible the survival of flora and fauna in times of ice ages and allowed for post-glacial re-colonization. Different types of glacial refugia can be distinguished, namely nunatak, peripheral and lowland refugia. Glacial refugia have been suggested as a major cause of the patterns of distributions of flora and fauna in both temperate and tropical latitudes. With respect to disjunct populations of modern-day species distributions, especially in birds, doubt has been cast on the validity of such inferences, as much of the differentiation between populations observed today may have occurred before or after their restriction to refugia. In contrast, isolated geographic locales that host one or more critically endangered species are generally uncontested as bona fide glacial refugia.

Ran Nathan is an Israeli biologist, ornithologist, and academic.

Diplochory, also known as “secondary dispersal”, “indirect dispersal” or "two-phase dispersal", is a seed dispersal mechanism in which a plant's seed is moved sequentially by more than one dispersal mechanism or vector. The significance of the multiple dispersal steps on the plant fitness and population dynamics depends on the type of dispersers involved. In many cases, secondary seed dispersal by invertebrates or rodents moves seeds over a relatively short distance and a large proportion of the seeds may be lost to seed predation within this step. Longer dispersal distances and potentially larger ecological consequences follow from sequential endochory by two different animals, i.e. diploendozoochory: a primary disperser that initially consumes the seed, and a secondary, carnivorous animal that kills and eats the primary consumer along with the seeds in the prey's digestive tract, and then transports the seed further in its own digestive tract.

<span class="mw-page-title-main">Glacial survival hypothesis</span>

According to the northern cryptic glacial refugial hypothesis, during the last ice age cold tolerant plant and animal species persisted in ice-free microrefugia north of the Alps in Europe. The alternative hypothesis of no persistence and postglacial immigration of plants and animals from southern refugia in Europe is sometimes also called the tabula rasa hypothesis.

Victoria Louise Sork is an American scientist who is Professor and Dean of Life Sciences at University of California, Los Angeles. She studies tree populations in California and the Eastern United States using genomics, evolutionary biology and conservation biology. Sork is a Fellow of the American Association for the Advancement of Science.

Nonadaptive radiations are a subset of evolutionary radiations that are characterized by diversification that is not driven by resource partitioning. The species that are a part of a nonadaptive radiation will tend to have very similar niches, and in many cases will be morphologically similar. Nonadaptive radiations are driven by nonecological speciation. In many cases, this nonecological speciation is allopatric, and the organisms are dispersal-limited such that populations can be geographically isolated within a landscape with relatively similar ecological conditions. For example, Albinaria land snails on islands in the Mediterranean and Batrachoseps salamanders from California each include relatively dispersal-limited, and closely related, ecologically similar species often have minimal range overlap, a pattern consistent with allopatric, nonecological speciation. In other cases, such as certain damselflies and crickets from Hawaii, there can be range overlap in closely related species, and it is likely that sexual selection plays a role in maintaining species boundaries.

References

  1. 1 2 3 Reid, Clement (1899). The origin of the British flora. Gerstein - University of Toronto. London Dulau.
  2. 1 2 3 4 5 6 Clark, James S.; Fastie, Chris; Hurtt, George; Jackson, Stephen T.; Johnson, Carter; King, George A.; Lewis, Mark; Lynch, Jason; Pacala, Stephen; Prentice, Colin; Schupp, Eugene W. (January 1998). "Reid's Paradox of Rapid Plant Migration". BioScience. 48 (1): 13–24. doi: 10.2307/1313224 . JSTOR   1313224.
  3. 1 2 3 4 5 Clark, James S. (August 1998). "Why Trees Migrate So Fast: Confronting Theory with Dispersal Biology and the Paleorecord". The American Naturalist. 152 (2): 204–224. doi:10.1086/286162. ISSN   0003-0147. PMID   18811386.
  4. 1 2 Cruzan, Mitchell B.; Templeton, Alan R. (December 2000). "Paleoecology and coalescence: phylogeographic analysis of hypotheses from the fossil record". Trends in Ecology & Evolution. 15 (12): 491–496. doi:10.1016/s0169-5347(00)01998-4. ISSN   0169-5347. PMID   11114435.
  5. Powell, James A.; Zimmermann, Niklaus E. (February 2004). "Multiscale Analysis of Active Seed Dispersal Contributes to Resolving Reid's Paradox". Ecology. 85 (2): 490–506. doi:10.1890/02-0535. ISSN   0012-9658.
  6. Rull, Valentí (2010-06-21). "On microrefugia and cryptic refugia: Correspondence". Journal of Biogeography: no. doi: 10.1111/j.1365-2699.2010.02340.x .