Sympatric Speciation in the Post “Modern Synthesis” Era of Evolutionary Biology

Sympatric speciation is among the most controversial and challenging concepts in evolution. There are a multitude of definitions of speciation alone, and when combined with the biogeographic concept of sympatric range overlap, consensus on what sympatric speciation is, whether it happens, and its importance, is even more difficult to achieve. Providing the basis upon which to define and judge sympatric speciation, the Modern Evolutionary Synthesis (Huxley in Evolution: the modern synthesis. MIT Press, Cambridge, 1942) led to the conclusion that sympatric speciation is an inconsequential process in the generation of species diversity. In the post Modern Synthesis era of evolutionary biology, the PCR revolution and associated accumulation of DNA sequence data from natural populations has led to a resurgence of interest in sympatric speciation, and more importantly, the role of natural selection in lineage diversification. Much effort is currently being devoted to elucidating the processes by which the constituents of an initially panmictic population can become reproductively isolated and evolve some level of reproductive incompatibility without the complete cessation of gene flow due to geographic barriers. The evolution of reproductive isolation solely due to natural selection is perhaps the most controversial manner by which sympatric speciation occurs, and it is that which we focus upon in this review. Mathematical model simulations indicate that even strict definitions of sympatric speciation are possible to satisfy, empirical data consistent with sympatric divergence are accumulating, but irrefutable evidence of sympatric speciation in natural populations remains elusive. Genomic investigations are advancing our ability to identify genetic patterns caused by natural selection, thereby advancing our understanding of the power of natural selection relative to gene flow. Overall, sympatric lineage divergence, especially at the sub-species level, may have led to a substantial portion of biodiversity.     

Testing Models: A Key Aspect to Promote Teaching Activities Related to Models and Modelling in Biology Lessons?

This study investigated biology teachers’ (N = 148) understanding of models and modelling (MoMo), their model-related teaching activities and relations between the two. A framework which distinguishes five aspects of MoMo in science (nature of models, multiple models, purpose of models, testing models and changing models) served as a theoretical background. Teachers’ understanding of MoMo was assessed using constructed-response items which were analysed qualitatively based on a coding scheme. The biology teachers mainly expressed a limited understanding of models as copies or idealised depictions used to show or to explain something. Model-related teaching activities were assessed through rating-scale items. The findings propose that models are primarily generated in biology lessons to show or to explain something but are rarely contrasted with other models, evaluated and modified. Significant correlations between teachers’ understanding of the aspect testing models and their intensity of model-related teaching activities were found. This suggests that the aspect testing models is a key aspect of promoting teaching activities related to MoMo in biology lessons. The findings are discussed with respect to relevant literature about MoMo in science education and educational implications are provided.     

Evolutionary Trends in the Flowers of Asteridae: Is Polyandry an Alternative to Zygomorphy?

Background and Aims

Floral symmetry presents two main states in angiosperms, actinomorphy (polysymmetry or radial symmetry) and zygomorphy (monosymmetry or bilateral symmetry). Transitions from actinomorphy to zygomorphy have occurred repeatedly among flowering plants, possibly in coadaptation with specialized pollinators. In this paper, the rules controlling the evolution of floral symmetry were investigated to determine in which architectural context zygomorphy can evolve.

Methods

Floral traits potentially associated with perianth symmetry shifts in Asteridae, one of the major clades of the core eudicots, were selected: namely the perianth merism, the presence and number of spurs, and the androecium organ number. The evolution of these characters was optimized on a composite tree. Correlations between symmetry and the other morphological traits were then examined using a phylogenetic comparative method.

Key Results

The analyses reveal that the evolution of floral symmetry in Asteridae is conditioned by both androecium organ number and perianth merism and that zygomorphy is a prerequisite to the emergence of spurs.

Conclusions

The statistically significant correlation between perianth zygomorphy and oligandry suggests that the evolution of floral symmetry could be canalized by developmental or spatial constraint. Interestingly, the evolution of polyandry in an actinomorphic context appears as an alternative evolutionary pathway to zygomorphy in Asteridae. These results may be interpreted either in terms of plant–pollinator adaptation or in terms of developmental or physical constraints. The results are discussed in relation to current knowledge about the molecular bases underlying floral symmetry.Key words: Floral symmetry, architectural constraints, Asteridae, comparative analysis, composite tree, correlated evolution, evolutionary scenario     

“Force-Talk” in Evolutionary Explanation: Metaphors and Misconceptions

The notion of “pressure” as an evolutionary “force” that “causes” evolution is a pervasive linguistic feature of biology textbooks, journal articles, and student explanatory discourse. We investigated the consequences of using a textbook and curriculum that incorporate so-called force-talk. We examined the frequency with which biology majors spontaneously used notions of evolutionary “pressures” in their explanations, students’ definitions and explanations of what they meant when they used pressures, and the structure of explanatory models that incorporated evolutionary pressures and forces. We found that 12–20 percent of undergraduates spontaneously used “pressures” and/or “forces” as explanatory factors but significantly more often in trait gain scenarios than in trait loss scenarios. The majority of explanations using “force-talk” were characterized by faulty evolutionary reasoning. We discuss the conceptual similarity between faulty notions of evolutionary pressures and linguists’ force-dynamic models of everyday reasoning and ultimately question the appropriateness of force-talk in evolution education.     

Human–Tiger Conflict in Context: Risks to Lives and Livelihoods in the Bangladesh Sundarbans

People’s perceptions of the risk posed by wild animals to human lives and/or livelihoods can influence the rate at which people intentionally kill these species. Consequently, human–wildlife conflict (HWC) management strategies may benefit from the inclusion of actions which reduce risk perceptions. This study uses Participatory Risk Mapping (PRM) and semi-structured interviews to explore local perceptions and the wider socio-economic context of human–tiger conflict (HTC) in the Bangladesh Sundarbans area. Of the 24 locally-relevant problems identified by the PRM process, tigers were the only problem to be cited by >50 % of respondents. The ‘tiger problem’ was also perceived by villagers to be of relatively high severity. Negative perceptions of tigers in the Sundarbans communities are exacerbated by other locally-experienced poverty-related problems, as well cyclones, floods and soil erosion. Interactions between the problems experienced by villagers, including HTC, result in a complex ‘risk web’ which detrimentally affects lives and livelihoods and ultimately perpetuates poverty levels in the Sundarbans communities. This research demonstrates that PRM and in-depth, qualitative research can enhance understanding of the perceived magnitude and wider socio-economic context of risks from wildlife and aid the identification of risk perception management actions which may help to reduce the number of animals killed by people.     

Me,Myself, and Semiotic Function: Finding the “I” in Biology

This essay argues that stable, heritable, habituated semiotics on one scale of life allows for opportunism, origination, and the solving of novel problems on others. This is grounded in how interpretation is neither caused nor determined by its object, such that success at interpretation simply cannot be defined by any comparison between an interpretation and its object. Rather, an interpretation is a reciprocated incorporation of a living thing and its environment, and successful if it furthers the living, interpreting thing. By applying biosemiotic theory to seemingly disparate studies of parasitic infections (Jaroslav Flegr), autonomic nervous systems (Stephen Porges), and social change (Charles Tilly) as well as the classical pragmatic notion that biology, psychology and sociology are disparate approaches to the singular, radically continuous, and perennial question of who (or what) am I (Dewey, James, Mead). I argue that the distinction (e.g.,) between voluntary and autonomic behavior is but a ghost of older dualisms, the pseudo-contradictions of matter v. mind, body v. soul, but also self v. not self. Moreover, all such pseudo-contradictions (individual v. social, sensation v. response, parasite v. host, and etc.) are resolved as scale thick, self-similar examples of semiotic transaction wherein degeneration or habituation on one scale of life allows for generative or novel interaction on another.     

Selection and mutation in the “new” genetics: an emerging hypothesis

It has been anticipated that new, much more sensitive, next generation sequencing (NGS) techniques, using massively parallel sequencing, will likely provide radical insights into the genetics of multifactorial diseases. While NGS has been used initially to analyze individual human genomes, and has revealed considerable differences between healthy individuals, we have used NGS to examine genetic variation within individuals, by sequencing tissues “in depth”, i.e., oversequencing many thousands of times. Initial studies have revealed intra-tissue genetic heterogeneity, in the form of multiple variants of a single gene that exist as distinct “majority and “minority” variants. This highly specialized form of somatic mosaicism has been found within both cancer and normal tissues. If such genetic variation within individual tissues is widespread, it will need to be considered as a significant factor in the ontogeny of many multifactorial diseases, including cancer. The discovery of majority and minority gene variants and the resulting somatic cell heterogeneity in both normal and diseased tissues suggests that selection, as opposed to mutation, might be the critical event in disease ontogeny. We, therefore, are proposing a hypothesis to explain multifactorial disease ontogeny in which pre-existing multiple somatic gene variants, which may arise at a very early stage of tissue development, are eventually selected due to changes in tissue microenvironments.     

Pet Ownership and Human–Animal Interaction in an Aging Population: Rewards and Challenges

ABSTRACT

Older adults in most developed countries can now expect to live nearly 80 years without significant disability. To maximize the quality of the years after retirement, societies, governments, and organizations are seeking strategies to help older adults maintain their mental and physical health, and retain their independence. Increasingly, the impact of pet ownership and other forms of human–animal interaction in healthy aging are discussed and investigated. In the Western world, more than 50% of households own one or more pets. The popularity of pets means they are well positioned to provide opportunities for companionship and nurturance. Since social networks tend to decrease as people age, pets may fill some gaps. While it is common to read about the benefits of pets and human–animal interactions, pet ownership in older age is also related to challenges and animal welfare concerns. This paper aims to briefly review the benefits and then explore risks and challenges related to pet ownership in older adulthood. In addition, we present strategies for maintaining beneficial pet ownership and human–animal interaction for older adults.     

Inside the “African Cattle Complex”: Animal Burials in the Holocene Central Sahara

Cattle pastoralism is an important trait of African cultures. Ethnographic studies describe the central role played by domestic cattle within many societies, highlighting its social and ideological value well beyond its mere function as ‘walking larder’. Historical depth of this African legacy has been repeatedly assessed in an archaeological perspective, mostly emphasizing a continental vision. Nevertheless, in-depth site-specific studies, with a few exceptions, are lacking. Despite the long tradition of a multi-disciplinary approach to the analysis of pastoral systems in Africa, rarely do early and middle Holocene archaeological contexts feature in the same area the combination of settlement, ceremonial and rock art features so as to be multi-dimensionally explored: the Messak plateau in the Libyan central Sahara represents an outstanding exception. Known for its rich Pleistocene occupation and abundant Holocene rock art, the region, through our research, has also shown to preserve the material evidence of a complex ritual dated to the Middle Pastoral (6080–5120 BP or 5200–3800 BC). This was centred on the frequent deposition in stone monuments of disarticulated animal remains, mostly cattle. Animal burials are known also from other African contexts, but regional extent of the phenomenon, state of preservation of monuments, and associated rock art make the Messak case unique. GIS analysis, excavation data, radiocarbon dating, zooarchaeological and isotopic (Sr, C, O) analyses of animal remains, and botanical information are used to explore this highly formalized ritual and the lifeways of a pastoral community in the Holocene Sahara.