**1. Introduction**

116 Genetic Diversity in Plants

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The Brazilian Atlantic Forest biome contains a high level of genetic diversity and endemic species. In the Atlantic Forest of Northeastern Brazil (Figure 1), habitat loss and fragmentation are the major threats to biodiversity. The degree of degradation of these areas is even greater than that observed in other regions of Brazil (Kimmel et al. 2008). These remnants are only 2% of the original forest area and are mostly restricted to private areas. These forest remnants shelter many native bromeliad species that are threatened with extinction.

Theoretically, population changes associated with habitat degradation lead to an erosion of genetic variation and increased interpopulation genetic divergence due to increased random genetic drift, elevated inbreeding, and reduced gene flow, where remnant/population size and isolation fall below critical levels. These changes are also predicted to affect population viability in the short and long term. In the short term, disturbed plant populations are expected to suffer increased disease and pest susceptibility, loss of incompatibility alleles, and fixation of deleterious alleles. In the long term, loss of genetic variation is expected to reduce the ability of populations to respond to changing selection pressures (Lowe et al. 2005).

The objective of this work was to study the genetic diversity and structure of *Aechmea fulgens* populations through SSR and ISSR molecular markers. Three populations from different remnants of Atlantic Rainforest in Pernambuco state, located in the northeastern region of Brazil, were comparing regarding the level of polymorphism and other populational parameters.

#### **1.1 Bromeliad history**

Bromeliads are typical plants of the American continent and probably originated in the Andean region. The species spread out throughout the millennia and reached the tropical forest about 200,000 years ago. In this taxonomic group, 2700 species were described, all native to the American continent except for a single species, *Pitcairnia feliciana*, which is found in West Africa (Benzing 2000).

Fig. 1. General view of an Atlantic Forest remnant in Northeastern Brazil. Igarassu, Pernambuco

Both terrestrial and epiphyte bromeliad are found even in the most desert and arid regions of the world. Bromeliaceae is subdivided into three sub-families: Bromelioideae, Tillandsioideae and Pitcairnioideae. It is estimated that about 40% of the species dwell in Brazil, many of which are endemic and concentrated mainly in the Atlantic Forest biome (Leme and Marigo 1993).

The bromeliads, being mostly epiphytes, depend on the forest conservation. The devastation process of the Atlantic Forest biome is the main cause of the genetic erosion of the bromeliad species. Only 18.06% of this forest is maintained in form of dispersed fragments in its associated ecosystems (Fundação SOS Mata Atlântica 2001).

The dynamics of tropical forest destruction have led to serious alterations in the ecosystems that compose the respective biomes due in particular to the high fragmentation of the habitats and to genetic erosion (Heringer and Montenegro 2000), making the establishment of germplasm conservation programs necessary and urgent.

#### **1.2** *Aechmea fulgens*

The *Aechmea* genus has significant representation in Pernambuco state where there are 22 species distributed in different environments (Forzza et al. 2010). The *Aechmea fulgens* Brongn. species deserves attention as a plant with economic value because of its ornamental potential. These species belongs to the Bromelioidea subfamily, Bromeliaceae family, and has epiphyte and soil habit and also occurs on rock outcrops. It can be found in the Atlantic Rainforest from Pernambuco, Bahia as far as Rio de Janeiro. In Atlantic Rainforest the bromeliads account for about 30% of the food resources used by hummingbirds and bats (Sazima et al. 1999). In spite of its great importance for tropical forests, little is known about the reproductive biology of the Bromeliaceae family (Balke et al. 2008). Some species of this family have mechanisms that favor cross pollination, but most are self incompatible. These processes are frequently associated to pollination by vertebrates (Fleming et al. 2009).

The ornamental value and lack of commercial production of the species has led to aggression against the native forests, from where great quantities are collected for commercialization on the domestic and foreign markets. Anthropological action and habitat fragmentation are the greatest causes of erosion of the biodiversity of tropical forests (Schaffer and Prochnow 2002).

The preservation of genetic diversity is one of the main objectives of conservation programs and the first step is knowledge of the distribution of this diversity within and among natural populations (Han et al. 2009). The most important characteristics in population genetics include understanding the gene flow and the genetic diversity and structure, because they are considered essential in the formulation of management and conservation strategies.

#### **1.3 Molecular markers**

118 Genetic Diversity in Plants

forest about 200,000 years ago. In this taxonomic group, 2700 species were described, all native to the American continent except for a single species, *Pitcairnia feliciana*, which is

Fig. 1. General view of an Atlantic Forest remnant in Northeastern Brazil. Igarassu,

associated ecosystems (Fundação SOS Mata Atlântica 2001).

of germplasm conservation programs necessary and urgent.

Both terrestrial and epiphyte bromeliad are found even in the most desert and arid regions of the world. Bromeliaceae is subdivided into three sub-families: Bromelioideae, Tillandsioideae and Pitcairnioideae. It is estimated that about 40% of the species dwell in Brazil, many of which are endemic and concentrated mainly in the Atlantic Forest biome

The bromeliads, being mostly epiphytes, depend on the forest conservation. The devastation process of the Atlantic Forest biome is the main cause of the genetic erosion of the bromeliad species. Only 18.06% of this forest is maintained in form of dispersed fragments in its

The dynamics of tropical forest destruction have led to serious alterations in the ecosystems that compose the respective biomes due in particular to the high fragmentation of the habitats and to genetic erosion (Heringer and Montenegro 2000), making the establishment

The *Aechmea* genus has significant representation in Pernambuco state where there are 22 species distributed in different environments (Forzza et al. 2010). The *Aechmea fulgens* Brongn. species deserves attention as a plant with economic value because of its ornamental

found in West Africa (Benzing 2000).

Pernambuco

(Leme and Marigo 1993).

**1.2** *Aechmea fulgens*

The polymerase chain reaction (PCR) based on molecular markers such as microsatellite (SSR) and inter-simple sequence repeats (ISSR) are being extensively used to study the genetic diversity in a number of plant species at the species as well as cultivar level. To date, no report is available on applications of molecular markers in studies on the genetic diversity in *Aechmea fulgens* populations. In this investigation, a first attempt was made to study the genetic diversity among three populations of *A. fulgens* using SSR and ISSR markers.

The Microsatellites or SSR (simple sequence repeats) and ISSR (inter-simple sequence repeats) marker methodologies have been widely used in studies with plant populations. ISSR involves amplification of DNA segments present at an amplifiable distance in between two identical microsatellite repeat regions oriented in opposite direction. The technique uses microsatellites as primers in a single primer PCR reaction targeting multiple genomic loci to amplify mainly ISSR of different sizes. ISSRs exhibit the specificity of microsatellite markers, but need no sequence information for primer synthesis enjoying the advantage of random markers ISSR markers usually show high polymorphism although the level of polymorphism has been shown to vary with the detection method used. SSR markers often present high levels of inter- and intra-specific polymorphism, particularly when tandem repeats number is ten or greater. SSRs have been the marker of choice in most areas of molecular genetics as they are highly polymorphic even between closely related lines, require low amount of DNA, can be easily automated for high throughput screening, can be exchanged between laboratories, and are highly transferable between populations. SSRs are mostly codominant markers, and are indeed excellent for studies of population genetics and mapping (Semagn et al. 2006).
