Evolution Of Lice

Lice are obligate parasites that reside on mammalian hosts. The evolution of lice is

very closely linked with changes in their host organisms, providing an excellent example of

coevolution between parasites and their hosts. Patterns of host migration can be support

and better understood by studying lice. Studying lice’s sensitivity to host environment,

geographic distribution, and genetic mechanisms of evolution can assist in studying any

respective host.

HOST SENSITIVITY

Being highly specific to their host is a basic feature of most successful parasites. Lice

are no exception to this rule. While there is conversation if human head and body lice and

separate species, there is a high degree of niche and species specificity in

Using

current estimations of mutation, it is not possible for current Pediculus humanus lineages to

be as genetically diverse as they currently are after such a bottlenecking event on their only

host. There are lines of evidence that Pediculus humanus was present on other non-human

species that were not declining in number, then, switching back to humans as their host

once the populations stabilized (Ashfaq et al. 2015). This is not the sole example of lice

switching hosts. Several multidimensional studies have confirmed that current lineages of

primate lice have actually jumped between gorillas and humans in several points in

evolutionary history, with cospeciation occurring in between these host switching events

(Reed et al. 2007, Light and Reed 2009). Lice are incredibly sensitive to changes in host

population and switching hosts is an excellent example of the lengths parasites will go to in

order to survive.

There is a rich history of study and debate over the phylogenetic, morphogenic,

ecological, and genetic differences between human head lice (Pediculus humanus

2009). In addition, the genes on these mini chromosomes have many repetitive

sequences. These lines of evidence suggest that these small pieces of mtDNA frequently

undergo recombination, contributing towards a wide array of genetic variation in lice.

Alternative splicing patterns also may contribute to lice and host coevolution.

Through the sequencing of over 400,000 human head and body lice transcripts, research

supports that the exclusion of certain exons from specific genes may help explain the rapid

divergence of lice species (Tovar-Corona et al. 2015). In addition, alternative splicing

patterns are common mechanisms of evolution in many species (Nilsen and Graveley

2010). Finally, both nuclear and mitochondrial genomes of lice are shown to have higher

rates of DNA substitution than both chimpanzees and humans (Johnson et al. 2014). These

lines of evidence support the idea that lice have the genetic means to evolve quickly to their

specific hosts. However, it cannot be overlooked that while parasites evolve, their hosts,

especially humans, are coming up with ways to rid themselves of these blood-sucking

parasites.

Lice and host coevolution give insight into each individual species’ evolutionary