Transcript The (Indirect) Costs of Conducting Research: A study of

Molecular Phylogeny of the Pectinidae Family
Jill Hansen, Lou Puslednik, and Jeanne Serb
Ecology, Evolution, and Organismal Biology, Iowa State University, Ames Iowa
Behavior Categories
Abstract
Scallops, part of a large bivalve family, are an economically
important group of organisms found worldwide. Species fall
into a variety of life styles: swimming, byssally attached to
hard substrates, recessing, nesting, gliding, and cemented to
rocks. Pectinid shell shape is highly correlated with behavior,
but this does not reflect phylogenetic relationships. Using
mitochondrial and nuclear gene analysis, the goal of this lab
is to analyze behavioral characteristics in an evolutionary
context. Data has revealed to date multiple, independent
origins of key behaviors and is challenging the assumptions of
the current morphologically based classification system.
Methods
Byssal attachment
Recessing
Free living
Gliding
Cementing
Nesting
Research Question
Background
The members of the family Pectinidae, commonly known as
scallops, live in a wide range of habitats from shallow waters
to abyssal zones and from tropical to polar regions. Of the
350 extant filter feeding species, some are free living and
swim to escape predators. Other forms are byssate, either as
juveniles or throughout life, and other still live cemented to
rocks as adults. Due to this wide variety of habitats, many
behaviors are observed with regards to life history. The origin
of complex traits is a major focus of evolutionary biology as a
unique behavior may be a key innovation for a group
providing for diversification and radiation of lineages.
Understanding the sequence of evolutionary traits is critical
to understanding when behaviors appear and diversify.
Current classification is morphologically based which does
not indicate the independent origins and evolutionary history
of traits. Although there is a large body of classification
literature, to date no one has placed behavioral traits in an
evolutionary framework. Owing to the development of
advanced sequencing techniques in molecular biology, it has
become feasible to gather large amounts of genetic data to
estimate phylogenies. Although it is possible to determine the
entire genome of a species with a specific behavior, including
multiple taxa in a genetic sampling provides a more valid and
robust phylogeny.
The goal was to use mitochondrial, nuclear ribosomal, and protein-coding
gene sequences to generate robust phylogenetic hypotheses for pectinid
scallops. Data generated will identify ancestral versus derived behaviors and
behaviors associated with lineage diversification and speciation.
Parsimonious Tree of Pectinidae
Samples were provided from a collaborator in Japan from
various localities and habitats. Qiagen kits were used to
extract genomic DNA from adductor muscles of 26 species
representing 15 genera with a variety of behaviors. DNA
from 12S and 16S (mitochondrial rRNA), 28S (nuclear
rRNA), and H3 (nuclear rRNA) genes were PCR amplified
using separate forward and reverse strand primers.
Amplification conditions were as follows: (35 cycles) 94°C
for 30 sec, 55°C for 30 sec, and 72°C for 60 sec. All
amplified fragments were checked by running a sample on
1% agarose gels. ExoSap cleanup reactions were used to
remove remaining single strand DNA and volumes were
adjusted with sterile water based on DNA concentration
through nanodrop analysis. Forward and reverse reactions
were completed simultaneously and dye was applied to
allow for fluorescent base analysis.
Sequencing was performed
at the ISU DNA Sequencing
and Synthesis Facility, using
an ABS 3730xl high throughput capillary system.
Sequence data was verified with Bio Editor and will be
applied to appropriate phylogenetic software to determine
evolutionary relationships.
Results
Although the ancestral scallop condition is ambiguous,
phylogenetic analysis to date has determined that there are at
least three independent origins of the gliding behavior (from
free living, recessing and undetermined behaviors), two
independent origins of recessing (free living and byssal
attaching ancestors), and two independent origins of cementing
(derived from byssal attachers). Onging work includes
correlation of behavior and morphology using 3D imaging and
determining convergence versus parallelism in shape and
behavior.
glider
recessing
free living
byssal attacher
cementer
Acknowledgements
nestler
References
“Evolution of behavioral traits in scallops (Bivalvia: Pectinidae)” Jeanne Serb.
“Scallops: Biology, Ecology and Aquaculture” SE. Shumway and G. Parsons
“Molecular phylogeny of the family Pectinidae (Mollusca: Bivalvia) based on
mitochondrial 16S and 12S rRNA genes” M. Barucca, E. Olmo, et al.
Thanks to Jeanne Serb for all of her guidance, support and
direction, Lou Puslednik for her patient explanations, and Terry
O’Dwyer, Autumn Pairett, and Kevin Roe for their invaluable
assistance. Also, thanks to Adah Leshem-Ackerman, Jay Staker,
Eric Hall, and Deb Christensen for all their work in the RET
program.