Introduction - Genetic Diversity in Establishing Plant Populations: Founder Number and Geometry - page 1

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CHAPTER

Introduction

Most plant species include somewhat isolated to completely isolated
populations that are established with low numbers of founders introduced
in different geometric patterns. Plants colonize remote habitats in a
wide variety of ways: one-seeded fruits blown on the wind, a seed bank
stimulated to grow by the opening of a canopy, a bat fl ying over a forest
defecating single seeds, concentrated multi-seed deposition in feces, and
the transport of multi-seeded fruits on animal coats are just a few examples
of means of dispersal that bring about a broad range of numerical and
spatial patterns by which species are introduced to unoccupied habitats.
Populations that differ in founder number and spatial establishment pattern
are likely to be on the increase as our ecosystems become more fragmented,
and where climate change may be driving the migration of populations.
However, we lack tools with which to analyse how number and patterning
of colonizers interact with other varying founding characteristics (such as
the genetic diversity of founders, population growth rates, and rates of seed
production) to affect population growth and genetic diversity retention. As
we consider these issues below, we refer to these types of interactions as
“spationumeric founding effects.”
Are such spationumeric differences in the founding of populations
important or not? For example, can moderate differences in the initial
geometry of the placement of the same number of founders signifi cantly
affect subsequent population growth and genetic diversity retention? If such
effects occur, how are they infl uenced by life history characteristics (e.g.,
bisexual versus dioecious individuals, annuals versus perennials, degree of
selfi ng, pollen and/or offspring dispersal distance)? How do the shapes of
preserves and corridors, or the placement of founders in different geometries
at varying distances from a suitable habitat border, affect population growth
and unique allele retention? How do the interactions of such factors affect
realized rates of inbreeding and population subdivision in populations?
How does the genetic diversity architecture of the source population from
which founders are derived infl uence the genetic variation in stands that
result from differing establishment conditions? Of what consequence are
such considerations for the evolution of populations and species?