Folmer Bokma - Academia.edu (original) (raw)

Papers by Folmer Bokma

The American Naturalist, 2014

Many studies have tried to identify factors that explain differences in numbers of species betwee... more Many studies have tried to identify factors that explain differences in numbers of species between clades against the background assumption that older clades contain more species because they have had more time for diversity to accumulate. The finding in several recent studies that species richness of clades is decoupled from stem age has been interpreted as evidence for ecological limits to species richness. Here we demonstrate that the absence of a positive age-diversity relationship, or even a negative relationship, may also occur when taxa are defined based on time or some correlate of time such as genetic distance or perhaps morphological distinctness. Thus, inferring underlying processes from distributions of species across higher taxa requires caution concerning the way in which higher taxa are defined. When this definition is unclear, crown age is superior to stem age as a measure of clade age.

When theologians inquired whether anything could be concluded about the creator from studying the... more When theologians inquired whether anything could be concluded about the creator from studying the creation, evolutionary biologist J.B.S. Haldane allegedly replied that the creator must have "an inordinate fondness for beetles", as there are more kinds of beetles than any other insect. One might similarly conclude that the creator is not particularly fond of the two species of colugo, which are sister to more than 350 primate species ), or the osprey, which is the single sister species to more than a hundred hawks and eagles (Sibley and Ahlquist 1990; Sibley and Monroe 1990).

Trends in Ecology & Evolution, 2000

Theory in Biosciences, 2010

The theory of punctuated equilibrium, which proposes that biological species evolve rapidly when ... more The theory of punctuated equilibrium, which proposes that biological species evolve rapidly when they originate rather than gradually over time, has sparked intense debate between palaeontologists and evolutionary biologists about the mode of character evolution and the importance of natural selection. Difficulty in interpreting the fossil record prevented consensus, and it remains disputed as to what extent gradual change in established species is responsible for phenotypic differences between species. Against the historical background of the concept of evolution concentrated in speciation events, we review attempts to investigate tempo and mode of evolution using present-day species since the introduction of the theory of punctuated equilibrium in 1972. We discuss advantages, disadvantages, and prospects of using neontological data, methodological advances, and the findings of some recent studies.

The American Naturalist, 2009

Recently, it has been shown with large data sets of extinct mammals that large-bodied lineages ex... more Recently, it has been shown with large data sets of extinct mammals that large-bodied lineages experienced higher speciation and extinction rates; with extant mammals, it has been shown that body size evolution is accelerated during speciation. Therefore, it is interesting to investigate whether mammalian body size evolution is faster in large-bodied lineages. Phylogenetic analysis assuming size-independent speciation rates suggested that the rate of body size evolution increases with body size, whereas size differences in recent sister species (that are little affected by species turnover) appear to be independent of size. This supports the hypothesis that high rates of species turnover increase the rate at which interspecific differences accumulate in large-bodied clades, whereas rates of evolution in single lineages are approximately size invariant. Similarly, these findings support the notion that mammalian body size evolution is indeed concentrated in speciation events.

Systematic Biology, 2013

Speciation and extinction rates can be estimated from molecular phylogenies. Recently, a number o... more Speciation and extinction rates can be estimated from molecular phylogenies. Recently, a number of methods have been published showing that these rates can be estimated even if the phylogeny is incomplete, that is, if not all extant species are included. We show that the accuracy of such methods strongly depends on making the correct assumptions about how the sampling process was performed. We focus on phylogenies that are incomplete because some subclades (e.g., genera and families) are each represented as a single lineage. We show that previous methods implicitly assumed that such subclades are defined by randomly (or in an extreme deterministic way) choosing the edges that define the subclades from the complete species phylogeny. We show that these methods produce biased results if higher taxa are defined in a different manner. We introduce strict higher level phylogenies where subclades are defined so that the phylogeny is fully resolved from its origin to time x(cut), and fully unresolved thereafter, so that for all subclades, stem age &amp;amp;amp;gt; x(cut) &amp;amp;amp;gt; crown age. We present estimates of speciation and extinction rates from a phylogeny of birds in which this subclade definition was applied. However, for most higher level phylogenies in the literature, it is unclear how higher taxa were defined, but often such phylogenies can be easily transformed into strict higher level phylogenies, as we illustrate by estimating speciation and extinction rates from a near-complete but only partly resolved species-level phylogeny of mammals. The accuracy of our methods is verified using simulations.

Proceedings of the Royal Society B: Biological Sciences, 2009

Proceedings of the Royal Society B: Biological Sciences, 2008

Is gradual microevolutionary change within species simultaneously the source of macroevolutionary... more Is gradual microevolutionary change within species simultaneously the source of macroevolutionary differentiation between species? Since its first publication, Darwin's original idea that phenotypic differences between species develop gradually over time, as the accumulation of small selection-induced changes in successive generations has been challenged by palaeontologists claiming that, instead, new species quickly acquire their phenotypes to remain virtually unchanged until going extinct again. This controversy, widely known as the 'punctuated equilibrium' debate, remained unresolved, largely owing to the difficulty of distinguishing biological species from fossil remains. We analysed body masses of 2143 existing mammal species on a phylogeny comprising 4510 (i.e. nearly all) extant species to estimate rates of gradual (anagenetic) and speciational (cladogenetic) evolution. Our Bayesian estimates from mammals as well as separate sub-clades such as primates and carnivores suggest that gradual evolution is responsible for only a small part of body size variation between mammal species.

Journal of Evolutionary Biology, 2010

According to Cope's rule, lineages tend to evolve towards larger body size, possibly beca... more According to Cope's rule, lineages tend to evolve towards larger body size, possibly because of selective advantages of being large. The status of Cope's 'rule' remains controversial as it is supported in some but not all large-scale fossil studies. Here, we test for Cope's rule by Bayesian analyses of average body masses of 3253 extant mammal species on a dated phylogenetic tree. The data favour a model that does not assume Cope's rule. When Cope's rule is assumed, the best estimate of its strength is an average ancestor-descendant increase in body size of only 0.4%, which sharply contrasts with the 9% bias estimated from fossil mammals. Thus, we find no evidence for Cope's rule from extant mammals, in agreement with earlier analyses of existing species, which also did not find support for Cope's rule.

Global Ecology and Biogeography, 2006

Aim To test the 'more individuals hypothesis' as a mechanism for the positive association between... more Aim To test the 'more individuals hypothesis' as a mechanism for the positive association between energy availability and species richness. This hypothesis predicts that total density and energy use in communities is linearly related to energy availability, and that species richness is a positive function of increased density. We also evaluate whether similar energy-density patterns apply to different migratory groups (residents, short-distance migrants and tropical migrants) separately.

Forest Ecology and Management, 2004

Responses to climate change will include changes in species composition, but adaptation through g... more Responses to climate change will include changes in species composition, but adaptation through genetic change may also be possible. The response to selection depends on the availability of additive genetic variation and the strength of selection. We found that Finnish ...

Evolution, 2012

Recent studies indicate that Neanderthal and Denisova hominins may have been separate species, wh... more Recent studies indicate that Neanderthal and Denisova hominins may have been separate species, while debate continues on the status of Homo floresiensis. The decade-long debate between &amp;amp;amp;amp;amp;amp;amp;quot;splitters,&amp;amp;amp;amp;amp;amp;amp;quot; who recognize over 20 hominin species, and &amp;amp;amp;amp;amp;amp;amp;quot;lumpers,&amp;amp;amp;amp;amp;amp;amp;quot; who maintain that all these fossils belong to just a few lineages, illustrates that we do not know how many extinct hominin species to expect. Here, we present probability distributions for the number of speciation events and the number of contemporary species along a branch of a phylogeny. With estimates of hominin speciation and extincton rates, we then show that the expected total number of extinct hominin species is 8, but may be as high as 27. We also show that it is highly unlikely that three very recent species disappeared due to natural, background extinction. This may indicate that human-like remains are too easily considered distinct species. Otherwise, the evidence suggesting that Neanderthal and the Denisova hominin represent distinct species implies a recent wave of extinctions, ostensibly driven by the only survivor, H. sapiens.

Ecography, 2001

nen, M. 2001. Random processes and geographic species richness patterns: why so few species in th... more nen, M. 2001. Random processes and geographic species richness patterns: why so few species in the north? -Ecography 24: 43 -49.

BMC Evolutionary Biology, 2011

Background: An important objective of evolutionary biology is to understand the processes that go... more Background: An important objective of evolutionary biology is to understand the processes that govern phenotypic variation in natural populations. We assessed patterns of morphological and genetic divergence among coastal and inland lake populations of nine-spined stickleback in northern Sweden. Coastal populations are either from the Baltic coast (n = 5) or from nearby coastal lakes (n = 3) that became isolated from the Baltic Sea (< 100 years before present, ybp). Inland populations are from freshwater lakes that became isolated from the Baltic approximately 10,000 ybp; either single species lakes without predators (n = 5), or lakes with a recent history of predation (n = 5) from stocking of salmonid predators (~50 ybp).

BMC Biology, 2007

Background: Plants, plant-feeding insects, and insect parasitoids form some of the most complex a... more Background: Plants, plant-feeding insects, and insect parasitoids form some of the most complex and species-rich food webs. According to the classic escape-and-radiate (EAR) hypothesis, these hyperdiverse communities result from coevolutionary arms races consisting of successive cycles of enemy escape, radiation, and colonization by new enemy lineages. It has also been suggested that "enemy-free space" provided by novel host plants could promote host shifts by herbivores, and that parasitoids could similarly drive diversification of gall form in insects that induce galls on plants. Because these central coevolutionary hypotheses have never been tested in a phylogenetic framework, we combined phylogenetic information on willow-galling sawflies with data on their host plants, gall types, and enemy communities.

Biological Journal of the Linnean Society, 2009

... Our phylogeny is largely based on the phylogeny of Ware, May &amp; Kjer (2007) of hig... more ... Our phylogeny is largely based on the phylogeny of Ware, May &amp; Kjer (2007) of higher Libelluloidea, which contains 22 of the 26 species analysed in the present study. Placement of Aeschna grandis and Anax junius was taken from Misof et al. ...