The Biology of Microalgae - Biotechnological Applications of Microalgae - page 12

taxonomic groups have been revealed. Formal analyses of species borders have
been made possible due to modern advances in techniques for sequence-based spe-
cies delimitation (Wiens, 2007; Zhang et al., 2008). A variety of methods for detect-
ing species are based on analytical character variation limits from DNA sequence
data. Hence, these methods are rooted in phylogenetic species insight, aggregating
a population that lacks separate variations into a single species, and distinguish-
ing other species by distinct nucleotide differences (Wiens and Penkrot, 2002;
Monaghan et al., 2005). Among these methods, statistical parsimony (Templeton
et al., 1992) segregates a group of sequences if genotypes are connected by long
branches that are affected by homoplasy. In recent times, the maximum likeli-
hood approaches aim to connect between statistics and sequence data by analyz-
ing the dynamics of lineage branching in phylogenetic trees for determining the
species boundaries. This technique attempts to determine the point of transition
from species-level (speciation) to population-level (coalescent) evolutionary pro-
cesses (Pons et al., 2006; Fontaneto et al., 2007). The similar morphological or
polymorphic traits of many algal groups that can be achieved by sequence-based
identification are, in fact, valuable discoveries in this field (Harvey and Goff, 2006;
Lilly et al., 2007; Vanormelingen et al., 2007). The taxonomy of the most common
microalgal species is sorted using available distributional information that is reli-
able. The distribution records, along with physiological information, will allow for
designing ecological models incorporating the special effects of climatic param-
eters, which in turn would be very useful to predict transfer in distribution due to
climatic changes. At present, such models are nonexistent for microalgae. As a
general conclusion, the biogeography of algae is a poorly explored area, but holds
great potential for exciting research and is definitely worthy of much greater inter-
est than received thus far.
2.4 HABITATS
Microalgal biodiversity or the variation in life forms within a given ecological region
is often considered the measure of a specified ecosystem. Biodiversity indicates not
only the species abundance of the area, but also the sum of the genera, species, and
ecosystems of a region. The water bodies in these diverse habitats harbor a wide vari-
ety of microalgae that appear, disappear, and reappear during the changing seasons.
2.4.1 F reshwater
Algae present in various freshwater habitats such as ponds, puddles, lakes, agricultural
lands, oxidation ponds, streams, canals, springs, water storage tanks, reservoirs,
and rivers are described and enumerated. Sub-aerial algae that transpire on moist
tree barks, the walls of buildings, and dripping rocks are also considered freshwa-
ter algae by various algologists. The information on freshwater algae is vast, yet
remains scattered. Blue-green algae, green algae, diatoms, and euglenoid flagellates
are the main components of freshwater habitats. There are also other types, such as
planktons (free floating), benthons (attached to sediments), epiphytic algae (attached
to larger algae and hydrophytes), epilithic algae (on stones and rocks of reservoirs