What is the Best “Collecting” Strategy for an Arthropod Museum?
A species consists of a population made up of individuals. Much information about a species can be found in one specimen (especially morphology). However, information about a population (=variation) requires many specimens that exhibit the ranges of morphological and genetic variation, distribution, phenology, etc.
Considering that resources are limited, what’s a curator to do? Maximize number of species for morphological vouchers, or maximize specimens of a particular species to create a robust representation of the population?
Do both! Get pretty much everything.
Long answer 1:
When trying to identify an unknown, even a single identified specimen can be incredibly helpful. Endeavors that benefit greatly from even a single specimen include classes, key creation, field guides, voucher collections (physical and photographic), checklists, etc. So maximizing species has benefits.
Most arthropod collections have geographic and taxonomic strengths/biases (see this brilliant paper: Ferro and Flick 2015), that is, they are often dominated by local specimens. (How overlap between “museum range” and species range affects our understanding of a species’ distribution is an interesting idea, but not for this essay.) Retaining a large number of specimens of local species may add greatly to the overall understanding of a species’ population, after all, who else should be collecting these beasts? So maximizing specimens of species has benefits.
Perhaps the best way to answer the question is to consider its inverse: What shouldn’t a curator do? Which specimens are of the least value?
(Generally speaking!) The specimen that carries the most morphological information is the singleton. Every other specimen of that species provides less and less morphological information, they only contribute information on variation. The specimens that provide the most population information are the outliers (geographic, temporal, etc.) because they help define extremes. Therefore, the specimens that carry the least information represent a species, life stage, time, AND place that is already represented by another specimen in the collection.
Specimens of the same species collected at the same time and place are often called a “series”, usually defined as 5, 10, or 20 individuals. A series is an important tool for the arthropod collection. It assures that plenty specimens are collected to account for breakage, individual variation, sexes, cryptic species, and abnormal abundance of rare species. But a series can go too far (this is less true for alcoholic preservation where 50 specimens may take up no more room than one). Maybe pointing 100+ ptillids from a single litter sample, or 1000+ throscids from an emergence study is unnecessary (the author is guilty of both).
Perhaps the best strategy for a collection manager is to maximize both: 1) the number of species; AND 2) specimens of a particular species, but work to keep redundancy of those specimens below a maximum threshold, and therefore not squander resources on “lower value” specimens.
Long Answer 2:
Not long ago museums had exclusive (more or less) resources such as museum workers, specimens, literature, etc. A user had to travel to the collection to use the resource. And, even though it seems obvious, the collection either had the resource or it didn’t (getting the resource, even a paper, took time and money).
Digitization of information (and all that that entails) has changed the landscape of cost and access to materials. For example, to peruse The Canadian Entomologist a reader no longer needs to travel to a museum or library—and to possess The Canadian Entomologist a collection no longer needs to have actual copies. It makes little sense to purchase Volume 1 (1869) when it is available for free online. (I’m not saying don’t expand your library, just make wise decisions.)
For collections a “resource spectrum” has developed. One end consists of resources that are fully digitizeable and can be created, duplicated, and/or passed around with ease including specimen label data. The other end consists of those things which cannot be digitized: the smell of naphthalene, a rousing debate over lunch about whether termites are cockroaches, and above all, physical specimens.
Digital “shadows” of specimens can be created, label data, photographs, DNA, etc., but an actual specimen cannot. The cost of obtaining specimens will almost certainly increase with time. Paperwork associated with obtaining, transporting, depositing, and holding a specimen has increased greatly. (These delusional handicaps placed on researchers and institutions are an important and too often overlooked cost/impediment to collections and research, but that’s a topic for a different essay.) The point is, from the standpoint of a multigenerational collection, now is probably the best (cheapest) time to obtain specimens (and other non-digitizeable resources).
As was mentioned above, even a single specimen provides a lot of information about a species. Additionally, a collection either has a specimen, or it doesn’t. Borrowing a specimen from another institution costs time and money. (Enormous amounts compared the first edition of The Canadian Entomologist. Cost to download the first edition of The Canadian Entomologist = $0.00. Cost to mail a package = $10.00. Therefore mailing a specimen is infinity percent more costly than downloading a free paper. That’s just math.)
In this scenario, increasing species diversity is the best strategy for small or extremely resource-limited collections. Population level information, such as distribution, phenology, etc. can be supplemented through other online specimen-level databases (but beware! see paper cited above).
My overall proposal is that museums should ACTIVELY work to increase their taxonomic holdings AND actively work to help increase the taxonomic holdings of other museums.
Now is the cheapest time (cost will only increase in the future), and actual specimens have clearly emerged as the highest “value” artifacts in a collection (because they are non-digitizeable). It is not inappropriate to imagine a future where all midsized and larger museums have one or more representatives of every order or family of insect, arachnid, etc. known on the continent, or even representatives of every genus (or species of the smaller orders: the 13 smallest orders in NA north of Mexico have a total of 511 spp. Five specimens of each species = 2,555 specimens, or 0.2555% of a million specimen collection.)
Something to mull over…