ABSTRACT
In a world where increasingly powerful computers are becoming available and are being made use of in science, we reflect on their use in taxonomy. Taxonomy is where we witness a grand stage show run by the environment and how nature shapes diversity among living organisms. Taxonomy has experienced many problems throughout the history of mankind, including the cryptic species where the
interaction between the environment and genes is delicate and thus produces a variant with minimum genetic and/or morphological variations. The chapter aims to assess the use of the power of computers to help in the differentiation of sibling species, especially among insect vectors of human diseases, which is often important for developing effective vector control methods. 4.1 Cryptic Species: An IntroductionThe interaction between the environment and genes is always a hot topic. The environment shapes the biology of an organism, with various degrees of success, as some organisms disappear without a trace, while others succeed and thrive for a long time. The variations created by such interactions don’t always give birth to a new species; instead they, at times, create variants with minimum variations, either in the gene structure or in the morphology. Cryptic species are defined as two or more species that have been erroneously classified as one species because they are hard to distinguish on the basis of morphology alone. However, molecular or behavioral variations are possible ways to differentiate them. Sibling species (cryptic sister species) are always cryptic species. They are also morphologically indistinguishable. But the only difference is that sibling species are sister clades in modern phylogenetic relationships based on the alignment of molecular data (DNA or amino acid sequences), where that relationship is not necessary in cryptic species [1]. The existence of sibling species was recorded in the pre-Linnaean era. William Derham was credited as the first person to recognize sibling species among the bird genus Phylloscopus in 1718 [2]. Sibling species often provide useful systems in which to study the diversification events that occur during the process of evolution, because in many cases, but not all, they have evolved quite recently [3]. Sibling species have, by definition, a close phylogenetic relationship, but they no longer freely exchange genes with one another. This allows us to explore the biological species concept, which emphasizes reproductive isolation as a central part of the speciation process. Beyond this, the existence of sibling/cryptic species can affect conservation measures, as in the case of marine turtles [4], lemurs
[5], and amphibians [6]. Natural selection can play a significant role in driving the evolution of particular genotypes and phenotypes. “Ecological speciation” is the term often used to describe such a process when it leads to reproductive isolation between diverged populations and the generation of new species. Some environments appear to result in morphological stasis (the cessation of morphological change) in the evolution/speciation among species. Examples of this are found in extreme environmental conditions, such as the Arctic [7]) and areas of deep oceans [8]. The phenomenon of cryptic species cannot be resolved in these areas by morphology alone. Conversely, the persistence of high levels of variability, such as variation in shell colors within and among invertebrates such as land snails in northern Europe, does not appear to be explained by environmental selection alone despite its known influence on heat tolerance [9]. The widespread occurrence of sibling and cryptic species in insect vectors is well established, especially in anopheline mosquitoes, where the number of sibling species with different vectorial capacity has been documented [10]. Anopheles culicifacies and A. subpictus are classic examples where one or two specific sibling species have vectorial capacity and are attributed as the major vector in some part of the world. But the most interesting thing is some other sibling species has vector potential in different regions. Phlebotomus argentipes morphospecies A has the vector potential over species B in Sri Lanka, whereas it is the other way round in India. All these differences occur within the minimum morphological variances they possess. The role of the environment in shaping such differential biology in very closely related species is very subtle and subject to much scrutiny. Cryptic species are known to be common in insects that are vectors of human diseases. One complicating factor is that some sibling species occur in sympatry, where the environment is the same [11, 12]. They are good models for studying speciation because they have evolved relatively recently. Straightforward predictions about the environment changes that have governed those changes can also be made. The pattern of changes in either genotype and/or phenotype might be easy to understand in the otherwise normal speciation process.
