Primary Research Program: The Sierra Dome Spider (Neriene litigiosa: Linyphiidae)
For more than four decades I have used the Sierra Dome spider as a field and laboratory system for studying the fitness effects of
mate and sire selection by females, the functions of polyandry, and how sexual
selection shapes and maintains the development of individual differences in morphology, physiology, and behavior. These highly observable spiders live in
accessible webs, exhibit dramatic courtship and male-male contest rituals, and show significant size, lifespan, and complex behavioral variation
among individuals — features that make them ideal for connecting developmental biology to evolutionary theory.
The central question guiding my current work is how male and female spiders develop combinations of traits that together
maximize lifetime mating and fertilization success. In males, this means exploring how physical and physiological
condition, immune competence, disease exposure, and experience interact to produce distinctive behavioral
“personalities.” Females are sequentially polyandrous by nature and have two different mate selection mechanisms, one
for first mates and another for, typically, 1 to 3 seconday mates. Although males are dominant, females completely control whether
mating occurs, and they can decide the proportion of of each male's ejaculate they allow into their pool of stored sperm for later use in fertilizing eggs.
Females may seek a form of nonrandom limited strategic diversity amongst the males that sire their offfspring.
Moreover, the proportion of each male type that is optimal may vary amongst females and may shift year by year.
Complex and dynamic female choice likely provides part of the selective context in which a degree of fascinating
diversity of male sexual strategies and corresponding physical and personality profiles is maintained. Another factor
is yearly variation in the virulence of two rickettsial diseases that affect both sexes of the spider.
I cannot over-emphasize what a fine model system this species is for deep sexual selection studies and, in spite of the large amount of background information
on the system I have gathered since 1980, how much more there is to be discovered through continued observation and the use of modern technologies,
including molecular genetics. Many questions of theoretical interest are not mentioned here - let me tell you about them! I am incredibly eager
to support an avid and capable young investigator interested in continuing research on the Sierra Dome
spider as a major component of their career in evolutionary behavioral ecology.
Integrative development of male Sierra Dome spiders
Our current research emphasis is on individual development in males—the way that body form, physiological state, and
behavior are integrated through development to produce coordinated mating strategies. Each male can be viewed as a dynamic
system in which multiple traits—size, endurance, stridulation vigor, web use, risk taking, and immune profile—co-evolve
and co-adjust to one another. Selection favors combinations of traits that work well together rather than extremes of any
single feature.
This approach treats “personality” not as a metaphor but as a quantifiable, integrative phenotype: a repeatable
configuration of physical, physiological, and behavioral traits that together influence reproductive success. We ask how
these configurations arise during juvenile development and how environmental variables such as food, temperature,
parasites, and social encounters bias the trajectory toward one or another mature strategy.
Guarding and associative behavior in penultimate females
Penultimate female Sierra Dome spider guarded by a mature male, showing associative behavior
(see Watson 1990).
In the associative phase, a penultimate female remains close to a visiting male in the center of her dome,
eliciting multi-day guarding attempts that never occur with avoidant or mature females. Each arriving male
fights to replace the current guard, generating a sequence of contests that ends when the female molts and
mates immediately with the final resident—the “champion” male. This female-initiated dynamic, described in
Watson 1990,
illustrates how associative behavior enhances male–male competition and secures a high-quality first mate.
Current work examines a rapid “skipping” display by associative females that may intensify these combats.
NEW: Laser vibrometry of web-borne signals
In 2024 we began using laser vibrometry to record, in unprecedented detail, the vibratory signals that
males and females send to one another through their webs. The technique captures every major style of
strumming and vibration involved in both male–male contests and male–female interactions, including:
Abdominal twitching
Pedipalp twitching
Male four-legged pre-copulatory web-strumming
Female skipping
Female two-legged web-strumming
Female web-pulling and shaking
These high-resolution recordings allow us to compare individual males much as one might compare musicians performing the
same piece—each male produces the basic pattern, but with subtle differences in rhythm, intensity, and phrasing that
reflect his internal state and strategy. We are now quantifying how these signal “styles” correlate with body condition,
age, disease exposure, and ultimately mating and fertilization success.
Laser vibrometry provides a new, fine-grained window into how individual personality development is linked to mating
strategy and will become a major tool for the next phase of this long-term study.
Other Active Research Areas (Under Construction)
The evolution and potential adaptive function of unipolar depression
This section is currently under construction. Collaborators interested in this topic are welcome to make contact.
The evolution of religiosity
This section is currently under construction. Collaborators interested in this topic are welcome to make contact.
The efficacy of combining evolutionary psychology with introspective and meditative practices to accelerate a personal journey toward objective self-knowledge
This section is currently under construction. Collaborators interested in this topic are welcome to make contact.
Dr. Watson rock-sitting on the Maine coast, continuing explorations of human and non-human behavior
through evolutionary and introspective lenses.
