The Contribution Of Genetics To Our Understanding Of Ecological Problems

Genetics in ecology helps us to understand the dynamic relationship that genetic diversity has with conservation, by applying phylogenetics, and using this to aid the evolutionary potential of the genetic structure (Allendorf et al. 2013). By monitoring the genetic structure of a species, a conservation priority can therefore be established. For example, a species considered as monotypic will have a higher priority as it is more at risk of extinction, along with species that have a small population, consequently resulting to inbreeding, reducing the diversity and therefore meaning the species is susceptible to extinction (Frankham et al. 2010).

Molecular markers have allowed researchers to optimise the information that can be found surrounding a species, for example quantifying the amount of genetic diversity and monitoring the immigration of species, with more recent application providing an insight in to how the genes are functioning and adaptations that may be helping or impeding the species chance of survival (Freeland et al. 2011). This has led to the increase study of evolutionary and ecological functional genomics (EEFG) to further understand how genes and polymorphisms can be evolutionarily beneficial (Feder and Mitchell-Olds 2003).

Genetic variation occurs by mutation and recombination during the process of sexual replication (meiosis) leading to diversity. When the population decreases and inbreeding arises, harmful mutations eventuate which leave the population at risk. Studies have found that inbreeding has negative consequences on every aspect of reproduction and survival, with species exhibiting higher juvenile mortality (Frankham 2005). By understanding the genetics behind the phenotypes, better judgements can be made to benefit each individual species and the conservation efforts that are to be put in place.

In order to measure genetic diversity, different traits are studied including proteins, nuclear DNA and mitochondrial DNA amongst other attributes. The advantage to DNA samples opposed to using proteins is that they can be obtained non-invasively in small quantities. There is a universal barcode for individual species thereby identifying them and discovering new genetically different species. By barcoding, an individual’s relationships between taxa can also be established, however, this process is challenged by hybridization and gene flow (Bromham 2016).

Hybridization is the result of two genetically distinct species reproducing to produce an offspring of mixed ancestry, which can result in speciation (Abbott et al. 2013).

The use of genetics also contributes to the determination of sexes, especially when it is impossible to distinguish sexes out in the field. Knowing the number of females and males in a population is vital to predict future generation stability, and the possible altercations that could arise from a gender imbalance. Molecular prey identification can also help us to understand the diets of smaller predatory organisms, for example insects such as the Asian paper wasp (Polistes chinensis antennalis) which was studied by molecular diagnostics. This technique yielded more accurate identification of the prey than previous approaches and resulted in 42 taxa being identified as prey of the Asian paper wasp. (Ward and Ramón-Laca 2013). Accordingly, by the use of genetics ecologists can gain a deeper understanding of trophic levels and relationships between different species.

Further in this essay the concept of animal mating systems, using molecular data, to further explore the genetic relationships amongst individuals, along with identifying where a particular sample has originated, will be explored. It has been in more recent years that the study of behavioural ecology has moved towards molecular research opposed to laboratory-based observations. Samples are collected non-invasively for example using hair or feathers (any biological substance can be used), and the genotypes therefore generated meaning that parents of an individual can be identified by using population allele frequency data.

There are 5 main classifications for different mating systems between organisms; monogamy, polygyny, polyandry, promiscuity and polygamy. Monogamy is one male and female restricting mating with only each other either for one breeding season or longer, with often both parents caring for the offspring (Davies et al. 2012).

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Social monogamy is extremely rare in taxonomic groups, apart from birds, where 90% of species are monogamous as it is thought biparental care leads to a higher survival rate of young (Freeland 2011).

Monogamy can be beneficial in other species as well, for example the Western Australian Seahorse (Hippocampus sublengatus). In this study, microsatellite analysis of was performed to find the maternal and paternal genotype. It was discovered that the males mating with only one female within broods have a higher success rate of mating than the polygynous males, therefore it being beneficial to males to be monogamous as they have an increased number of broods, therefore yielding a higher number of offspring during their lifetime (Kvarnemo et al. 2000). The genetic profiling of the embryos has led to a further understanding of mating systems and the potential outcomes, which can be further explored and provide an increased understanding to the dynamics of mating systems.

Monogamy has been established in hammerhead sharks (Sphyrna tiburo), also using microsatellite DNA profiling, with an estimation of over 81% of sampled females genetically monogamous, however, this way of mating may have a negative impact on the sharks, as due to population decline from increased exploitation of fisheries targeting mainly the larger females, a high male-biased sex ratio has been created and consequently there will be a reduced population size as only one female and male will reproduce with each other (Chapman et al. 2004). The advancement of technology in this field is therefore advantageous to the hammerhead sharks, as without the knowledge of monogamous mating within the species, ecologists would be unaware of the increased threat to the sharks, and the ecological problems that they are facing, the study of genetics in this example has consequently contributed to the conservation of the species.

Polygamy is the most common animal mating system, as it is considered to be the most beneficial to both sexes as there is further access to resources from the opposite sex as well as the added contribution of receiving many pre-nuptial gifts. (Kvarnemo 2018).

Generally, polygyny (where one male breeds with multiple females) is favoured by males as this increases the chances of their genes being passed along to the next generation as the reproductive success will be higher with the more females that they mate with. It is predicted that the majority of mammalian species are polygynous as it is considered beneficial to females as a means of protection (Aloise King et al. 2011). Dominant males in group living species tend to have the highest reproductive success, a study of bonobos (Pan paniscus) by Gerloff et al., 1999 found through microsatellite analysis of faecal samples that the dominant bonobos and reproductive success have a positive correlation.

However polyandry, with females mating with more than one male, is favoured by some species, for example, the wattled jacana (Jacana jacana), females lay eggs for different males to fertilise, therefore increasing the genetic diversity of the different clutches and ensuring that there is a higher percentage of offspring surviving (Emlen, Wrege, Webster 1998). Females tend to take more consideration in to choosing a mate as in the majority of cases they invest more time and energy in to raising their offspring, therefore, the good genes hypothesis states that the mate which proves to have the highest fitness value and advantageous characteristics will be chosen (Freeland 2011).

This has led to lekking, where females and males aggregate in a particular area to choose a mate, particularly, the females choose a male who they believe has the most advantageous genes. For example, the black grouse (Tetrao terrix) males who were successful in fights were selected by the female and therefore overtime there will be an evolutionary change in the behaviour of the males to impress females. (Beebee and Rowe 2008). Along with behavioural changes, the appearance of males will also change leading to sexual dimorphism as certain characteristics are more valued than others, for example in peafowls (Pavo cristatus) the male peacock has a large plumage of feathers in vibrant colours to display during courtship.

Another hypothesis as to why females mate with multiple males is the genetic incompatibility theory, which states that the most compatible sperm to the females genotype will fertilise the eggs and therefore produce the most advantageous offspring (Zeh and Zeh 1997)

Every mating system in the ecosystem is different and due to molecular markers, these can be traced and identified to help with our insight into ecological problems, and how we can help to manage, conserve and maintain the natural environment along with the behaviours taking place within it. By having a deeper understanding of the genetics involved in the mating systems the costs and benefits of each classification can be identified and the evolutionary consequences of these actions.

References

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