When does a species evolve from another species, what is/are the signal (s), which determines that the genome differences can be packed into the same number of chromosomes or it needs to increase or decrease that number? Or is it a random process that happens by chance? Project proposal by: Ritika Goyal What is the signal a cell (and an organism on extrapolation) receives which tells it that it’s time to change its chromosome number to adapt to its environment and may be move on to the next species?

Understanding the problem... “It is not the kind of evidence where you can say that somebody has seen it happen, because it all happened a long time ago. It is more like a detective coming on to the scene of a crime after it has happened and piecing it together, and saying that all the clues point to a certain conclusion. Well, millions and millions of clues point to the truth of evolution.” Richard Dawkins

Species – the definition… Ernst Mayr’s biological species concept  "species are groups of interbreeding natural populations that are reproductively isolated from other such groups." Recognition species concept  “a species is a set of organisms that recognize one another as potential mates: they have a shared mate recognition system.” Phylogenetic species concept  “a species is the smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent."

Speciation –A three step process... Creation of a barrier to gene flow between populations Genetic & ecological divergence Reproductive isolation Gene flow Reproductive barrier Post-zygotic Environmental barriers Reproductive barrier Pre-zygotic Spatial Barriers

Is change in chromosome number that important for evolution of new species?

Solving the problem…. Studies on closely related species. Ring Species E. Eschscholtzii X E. klauberi Ensatina sp. No Interbreeding

E. klauberi E. oregonensis Plan of action… Study the differences between ; E. eschscholtzii o Phenotype o Behavioral differences o Habitat

Analysis of those differences  The molecular basis Genetic level Genes involved Changes in the expression pattern Protein level Changes in the structures of proteins Changes in levels of proteins Changes in the function of proteins Investigating the factors which might have led to the changes.

An example… Skin color Genes x, y & z Changes in expression pattern of these gene in different species Significance of the change Factors that might have led to this change

o E. croceator (A) o E. klauberi (B) o E. eschscholtzii (C) A BC x The key difference between A & B which led to the reproductive isolation of B making it a new species. The factors/signals which have led to that Difference or SPECIATION !

An Alternative Approach… Study of the relationship of genome structure and function across different biological species or strains. Both similarities and differences in the proteins, RNA, and regulatory regions of different organisms can be studied. The role of selection upon these elements can be inferred. Comparative Genomics

Future Aspects… Other ring species like Larus gulls can be studied. Other closely related species can be studied. All these data can be analyzed to find similarities in the process of speciation. Is there something common between all these during the course of speciation?

References

It’s hard to unravel the mystery of billions of years of evolution through a few years of research….. but this work can definitely lead us a step forward.