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189

DENVER MUSEUM OF NATURE & SCIENCE

REPORTS

|

No. 3, July 2, 2016

Student - oral presentation

Urban Islands: a biodiversity survey of

spiders on Portland, Oregon green roofs

Jessica Szabo, Susan Masta, Olyssa Starry

Portland State University Department of Biology PO

Box 751 Portland, Oregon 97207-0751, USA

szab@pdx.ed u

Urban development reduces green space and causes

fragmentation of natural habitats, reducing the con-

nectivity of populations of organisms. Green roofs

(rooftops with vegetation and shallow soil) may help to

augment green space in cities and provide connectivity

for plant and animal populations. Spiders are good

bioindicators of the health of an ecosystem; if spiders

are abundant in green roof communities, there is a

food source (typically arthropods) available to them,

signaling a thriving ecosystem. We surveyed the spider

community on 8 green roofs in Portland, Oregon, sam-

pling every two weeks from April through September

over two years. We examined whether plant composi-

tion on the green roofs influenced spider biodiversity

and abundance by comparing herbaceous and

Sedum

planted roofs. We found that herbaceous roofs had only

slightly higher abundance and diversity of spiders, but

that both types of roofs harbored different compositions

of spider species. The most abundant families found

overall were Linyphiidae, Thomisidae, Salticidae and

Gnaphosidae. Spiders in the family Linyphiidae are

known to balloon as adults, which may explain why

they are the most abundant family on every roof. Bal-

looning allows for greater dispersal and thus, greater

access to high places like tall buildings. Interestingly,

the green roof watering regime did not affect spider

biodiversity, as the unwatered herbaceous roof had

equivalent spider diversity to the watered roof. We

suggest that cities incorporate a diversity of green roofs,

including those with herbaceous and

Sedum

plant-

ings, and low to no additional water, to best maintain

arthropod biodiversity.

Keywords: ecoroof, urban ecology, spider ecology, pitfall

trap

Student - poster presentation

Last male paternity bias in

Tetragnatha

does intermating interval matter?

Kaitlyn Dodson Tatro, Autumn Alexis Richardson, Anne

Danielson-Francois

University of Michigan - Dearborn, Department of

Natural Sciences, 4901 Evergreen Road, Dearborn,

Michigan 48128, USA

ketatro@umich.edu

Long jawed spiders of the genus

Tetragnatha

have been

studied for their mating behavior, but few studies have

determined the paternity patterns found in these species.

Female reproductive morphology predicts that the last

male to mate should be favored in species with cul-de-sac

spermathecae, although other researchers have found either

extreme variability or a last-male bias for the first egg sacs

with an antichronological sequence of paternity for subse-

quent egg sacs. It has recently been demonstrated that males

can remove amorphous mating plugs composed of rival

male sperm. However, the influence of the age of the sperm

plug on the ability of males to remove it has not been tested.

Here, we used the classic sterile male technique to determine

whether or not paternity was influenced by the age of the

sperm plug in

Tetragnatha elongata

. Females were mated to

two males sequentially and assigned randomly to one of two

groups: presentation of the second male after either short

(15 min) or long (6 hour) intermating intervals. Across both

groups, we found a strong bias for last-male paternity in

the first egg sacs laid. Here, we report the paternity patterns

observed for subsequent egg sacs and the influence of the

intermating interval. We discuss the implications of our

findings for sperm competition in this species.

Keywords: sexual selection, sperm competition, sexual

behavior, paternity analysis

Oral presentation

Prey color biases, learning, and colorful

courtship in jumping spiders

Lisa Taylor

1

, Collette Cook

1

, Michelle Brock

1

, Michael

Vickers

1

, Nathan I. Morehouse

2

, Jeff Coco

1

, Lauren Gawell

1

,

Lauren Holian

1

1

Entomology and Nematology Department, University

20

th

International Congress of Arachnology