Living Species Overview

Overview of the Living Biota 

There is a rich and growing body of literature about biological life on islands. Some of the more notable publications are the pioneering but flawed volume by MacArthur and Wilson (1967), the wide-ranging and perceptive studies of Carlquist (1965, 1974), Lack’s (1976) insightful work for the West Indies, Quammen’s (1996) charming survey of many island systems, and Mayr and Diamond’s (2001) detailed look at the birds of northern Melanesia. “Biogeography is the study of the facts and patterns of species distribution. It is the science concerned with where animals are, where plants are, and where they are not” (Quammen, 1996:17). This book presents the authors’ modest attempt to provide a biogeographical look at Martha’s Vineyard, in the process of providing the best inventory we can muster of the living biota of the island.   

An almost revolutionary event in the history of taxonomy was the publication in 1982 of the first version of Margulis and Schwartz’s Five Kingdoms: an Illustrated Guide to the Phyla of Life on Earth. This publication has reshaped the classification of living things. There have been adjustments and refinements to even the most recent third edition (1998), especially in the nomenclature applied to many groups of insects. Where appropriate, we have adopted several of these changes and have provided the requisite references in places where we have departed from the original treatment. It is to be expected that there will be more refinements and changes in the future. But the concept incorporated in Five Kingdoms has already become the standard taxonomic structure for life on Earth

Of the five Kingdoms of living things identified by Margulis and Schwartz (1998), four have been documented on Martha’s Vineyard. The exception is Kingdom Bacteria. Obviously, bacteria are present here in incalculable numbers. In fact, these authors consider bacteria to be the dominant life form on the planet, being more abundant, indestructible, more diverse in biochemistry and present in a greater range of environments that all members of the other four Kingdoms combined (p. xiii). 

This book, however, is about the other four Kingdoms represented here. These four Kingdoms are broken into 82 phyla. As might be expected, we have a great deal more information about some phyla here than others. Two phyla are only represented by a single known non-introduced species (Phylum Myxomycota – Plasmodial Slime Molds, and Phylum Sphenophyta – Horsetails). In the first case, other species are surely present which have not yet been detected. In the second case, there may be no other species here. The reader will also find that there are many families of organisms present on the island for which we know of only a few species out of the total that are probably represented. 

In general, we have tried to present for the larger phyla the taxonomic categories down to the family level. We emphasize that there are many cases where experts disagree on the nomenclature at the family level or above. We do not present ourselves as experts in such nomenclatural matters and have relied on professional sources we consider scientifically respectable. 

 Twenty phyla of living organisms are treated in this book out of the 82 included by Margulis and Schwartz in the four Kingdoms that have representatives on the island. Each phylum has its own chapter, although some of those chapters are very brief. In the case of three phyla we have created subchapters for convenience, both ours and the reader’s. Most students of the insect order Lepidoptera, which includes both butterflies and moths, agree that butterflies are “nested” within the Lepidoptera as one proceeds from the most primitive moths to the most highly developed forms (see Goldstein essay). But because most people think of butterflies as day-flying and colorful in contrast to moths as night-flying and dull-colored, we have made a distinction here that is not actually warranted by the taxonomy. Indeed, there are nearly as many day-flying moth species in Massachusetts as there are butterflies. Also, among the insects, we have included sub-chapters for Scarab Beetles and Tiger Beetles despite the fact that both are subsets of the very much larger order of beetles (Coleoptera) with many other representatives on the island for which we do not have comparable information. We have also made a distinction between freshwater and marine crustaceans even though some of the same orders are included in each subchapter. Lastly, the general taxonomy of bony fishes does not make the distinction between marine and freshwater species given here, even though many people think of them as separate groups.

The foundation of all ecological systems is the plant community, both on land and in the sea. Nine phyla in Kingdom Plantae are found here. Plants are the substrate upon which virtually all organisms depend in one way or another. The essay below by Stephen Spongberg discusses the land-based flora and vegetation of the island in general, the number of species known to be present, lists those species that are threatened, endangered or of special concern, discusses introduced and invasive species, reviews the origin and phytogeographic relationships of the island flora and its vegetation history, and provides indicator plant species for 27 distinct plant communities.

An important conclusion that proceeds from Dr. Spongberg’s essay is the extent to which the flora has changed over time since the end of the last ice age. This is a theme reflected in many of the other chapters where there is enough information available to draw reasonable suppositions. As pointed out in the chapter on Geological History, there has been a series of glaciations that have influenced the plot of land that has become Martha’s Vineyard today, and it can be presumed that the vegetation found here has thus shifted with the prevailing climate several times. Our primary concern in this work, however, is the events of the last 5,000 to 6,000 years since what is now the island first became surrounded by the sea. 

 As pointed out in the Spongberg essay, as the climate warmed and habitats changed in the post-glacial period, new species invaded, altering the composition of the flora. In turn, new habitats permitted new species of all kinds of animals to survive here that could not have done so before. In short, conditions became less hospitable for tundra species and more so for species of plants and animals from the south or the adjacent continental land mass. 

It has been known for a long time that Martha’s Vineyard is in a transition zone between northern and southern habitat types due to its position near the north end of the Atlantic Coastal Plain. One of the objectives of this work has been to identify those groups of plants and animals present now whose overall distributions have a phytogeographical or zoogeographical bias toward the north, the south, or the nearby continent. In other words, to what extent can we say where the species present today probably originated? To the extent we are able, the bias of the plants or animals in each phylum is discussed in each chapter or subchapter. These biases can be summarized as follows:

Northern Bias 

Marine algae (Phaeophyta, Rhodophyta and Chlorophyta as a group)

Reptiles

Amphibians (native species only)

Mammals (pre-introduction fauna only)

                                           Southern Bias                                                

Butterflies

Moths

Odonates

Ants 

Cartilaginous Fish

Bony Fish (both Fresh Water and Marine species)

Birds

Ferns

Mosses

Liverworts

Continental Bias         

Flowering Plants

We find it interesting that there are as many groups as there are with a northern bias represented. Looking at these more closely we note that the three groups other than the marine algae probably have a northern bias because those populations were marooned here by the rising sea level. All three of those groups are mobile, and the continental populations of all three groups shifted northward during the last 5,000 years; but the species left behind here could not do so. The marine algae apparently have less of an ability to shift their populations, so today’s algal flora still represents a population more typical of earlier in the post-glacial period than do the land-based plants.

The groups of organisms whose populations have a southern bias are all highly mobile or spread by spores. Prevailing southwest winds for much of the year certainly assist the arrival of such spores from the south.  Thus members of all these groups are capable of adapting to changes in habitat conditions fairly briskly and presumably made use of the Coastal Plain primarily (some freshwater fish may be an exception) to invade or colonize northward as the prevailing climate warmed. As discussed in the Spongberg essay, the island’s population of flowering plants appears to have reached here primarily from the mainland.         

At present, we do not have enough information about the other phyla or groups of plants, fungi, or animals to make even an educated guess about their geographical affinities. Complicating factor, in addition to the lack of occurrence data, are two kinds of short-term changes in conditions on the island. The first is habitat changes brought about by human occupation of the land. The presence of indigenous people living on what is now the island for at least the last 9,000 years and possibly longer (see chapter on Archeology and Anthropology) probably had some effect on the habitat (clearing land by burning, etc.), though it was surely modest in the beginning. By the immediate pre-colonial period the resident indigenous population had risen to an estimated 3,000 persons and the amount of land cleared for farming was surely more extensive. In addition, there must have been significant pressure on wildlife resources such as shellfish, fish, and mammals to feed this number of people. But the most dramatic changes began with the arrival of the first European settlers in 1642, such that by the mid-1800s the island was largely deforested (see Spongberg essay). Also, a very large part of the island was heavily grazed by sheep and other domestic animals. Shaler (1888) reports that plowing, overgrazing, and forest fires had rendered 33,000 acres in the central and eastern parts of the island untillable by the time of his writing, over half the land area of the island! These changes, especially in such a relatively short time, must have greatly impacted the populations of many then-resident species of plants and animals. Indeed, it seems likely that entire populations of some butterflies, moths, odonates, fresh-water crustaceans, spiders, mosses, fungi, and some understory flowering plants may have been lost altogether. As reforestation occurred during the last 150 years, species in several of these groups have probably reestablished themselves, particularly those species that are mobile (butterflies, moths, possibly odonates), spread by ballooning (spiders), or spread by spores (mosses, ferns, fungi).

The second short-term influence on the habitat which has affected resident flora and fauna is weather. Though there has been a gradual warming trend to our climate for the post-glacial period as a whole, the pattern has not been smooth. For example, it is now known that there was a very warm climactic period about 1000 AD during which the Vikings colonized southern Greenland, grew fruit trees, had flocks of sheep there, and may have visited the Vineyard. Our island was certainly larger then than it is today, though the sea level may have been as high as it is now due to the warmer climate. By contrast, there have been two periods of very cold weather since the island was formed, the so-called “Little Ice Age” from 1100 to 1250 AD and the last twenty years of the 1800s when temperatures were much lower than they have been since 1970. It was during the latter period that Niagara Falls and Vineyard Sound both froze so solid that ox-drawn wagons were able to cross to the Vineyard from Woods Hole on the ice. Glaciers advanced and the sea level fell in both cases. In addition to general temperature changes, wet and dry climatic cycles have also affected Vineyard habitats.

 Another factor which has affected habitats on the island since it became one is the sea. It has been noted by authors as long ago as Banks (1911) and Latimer (1925) that the surrounding ocean ameliorates the island climate compared to that of the mainland. Temperatures are several degrees warmer in winter and cooler in summer, and rainfall is less than on the nearby mainland, recently averaging only 42-43 inches per year. The surrounding ocean also tends to keep the island cooler than the mainland in spring and warmer later into the fall. (See the chapters on Birds and Butterflies for the effect this has on the occurrence of species in these groups.) The extent to which the ocean cools the island in spring can be considerable. For example, there are parts of the State Forest where scrub oaks often do not leaf out until mid-June. Lastly, for obvious reasons, average air humidity is consistently higher on the island than the nearby mainland.  

The island’s climate has warmed on balance during the last 5,000 years. And as it has done so, a large part of the Coastal Plain that was above water at the height of the glacial period has been inundated as the sea level has risen. For perspective, it should be recalled that sea levels have fluctuated widely during the last million years. At the peak of the Wisconsinan Ice Age, the sea level was about 300 feet lower than today (see the Geology chapter). However, at several times earlier in the Holocene and Pleistocene, the sea level was as much as 60 feet higher than today due to a perfectly normal cycle of global warming, a fact that should be kept in mind during the current debate about global temperatures. At the peak of two or three interglacial warm periods, the Arctic and Antarctic ice caps were reduced to probably no more than 30% of their present size. 

As mentioned above and discussed in several chapters below, the Coastal Plain became an important route along which plants and animals colonized northward as the climate warmed. This raises the general subject of invasions and invasive species. The word “invasive” has a negative connotation in most contexts in the sense that species so described tend to out-compete and replace native species. However, only a little thought is required to see that, in a broad sense, invasions and colonizations are the same things but at different speeds. We tend to think of an invasion as a more short-term phenomenon and a colonization as a longer-term one. Gradual habitat change brought about by natural global warming is nothing more than a procession of short-term invasions over time. Invasions have been going on continuously for the past 5,000 years and continue today. Each past event has made a tiny change in the flora and fauna here leading to what we see around us now. 

While we have limited information about the pace of plant or other colonizations that have occurred over extended spans of time, we can document a number of recent invasions that are still under way. In addition to the names of twelve introduced invasive plants, the Spongberg essay provides an excellent list of the characteristics of invasive plants and gives lists of both introduced invasive plants and four species of native plants that behave as invasives. Similar characteristics can also be derived for other groups. Among those characteristics is often a pattern of very rapid population increase followed by a topping out of the population and then a decline to a more stable population level (Elton, 1958). The first phase occurs because a newly introduced species may have no predators or parasites to restrict its increase, but such predators and parasites, and even diseases, will eventually arise to make use of the new food source or host provided by the invader, reducing its population to a level in balance with other species in the habitat. A classic example of this pattern appears to be the case of the Striped Skunk (Mephitis mephitis) on the Vineyard after its reintroduction about 1960 (see Mammal chapter). Other island examples are periodict explosive increases in Spongy Moth (Lymantria dispar) and, in recent decades, Winter Moth (Operophtera brumata) populations. The almost exponential increase in the House Finch (Carpodacus mexicanus) population here and its subsequent decline to a lower level also fits this pattern. Elton (1958) provides specific examples of other insects, birds, mammals, crustaceans, a lamprey, and plants whose populations have followed this pattern, so it is a normal and expectable part of population change.     

Looking broadly at the phyla included in this book, we find examples of invasives from several phyla in addition to plants. In most cases these organisms arrived at the Vineyard pretty much on their own, although human agency may have been responsible for part of their move from their original native habitat. All of the species listed below are thought to have arrived here within the last thirty years, or in the case of native species, their numbers have greatly increased here in that period.

   Phylum               Species                                                                             Origin            

Chlorophyta    Green alga Codium fragile                                                       Native

Rhodophyta    Red alga Haemescharia hennedyi                                           Europe

Rhodophyta    Red alga Lomentaria clavellosa                                               Europe

Animalia         Winter Moth Operophtera brumata                                           Europe

Animalia         Spongy Moth Lymantria dispar                                                  Europe, Asia

Animalia         Japanese Beetle Popillia japonica                                             Asia 

Animalia         Giant Resin Bee Megachile sculpteralis                                    Asia

Animalia         German Wasp Vespa germanica                                               Europe 

Crustacea        Green Crab Carcinus maenas                                                  Europe

Crustacea        Asian Shore Crab Hemigrapsus sanguineus  (1996)                Asia   

Mollusca         Common Atlantic Slipper Crepidula fornicata                            Native  

Craniata          Turkey Vulture Cathartes aura                                                   Native 

Craniata          Great Horned Owl Bubo virginianus                                          Native 

Craniata          Chuck-wills-widow Caprimulgus carolinus                                 Native

Craniata          Red-bellied Woodpecker Melanerpes carolinus                        Native 

Craniata          Acadian Flycatcher Empidonax virescens                                  Native

Craniata          Tufted Titmouse Baeolophus bicolor                                          Native 

Craniata          Northern Mockingbird Mimus polyglottos                                   Native

Craniata          Northern Cardinal Cardinalis cardinalis                                      Native 

Craniata          House Finch Carpodacus mexicanus                                         Mexico

 

Looking at the native invasives, they fall into two categories: mobile species and relatively immobile species. The latter category includes the plants, the alga and perhaps the mollusk. Those species only need to invade successfully once in order to become established. The mobile species (moths, beetle, crabs and birds) may occur first as vagrants, then later appear more frequently, and finally occur regularly until they become established residents and breeders. Eventual establishment of a breeding population requires that appropriate habitat is present, so that has to come first. For the birds, when the pioneer population represents the northernmost extent of the species’ range, adverse weather conditions can occasionally eliminate or significantly reduce the resident population. Examples are the Common Barn Owl (Tyto alba), which has suffered complete extirpation or greater than 90% population declines twice in the last fifty years, and Carolina Wren (Thryothorus ludovicianus), an colonizer from the south that first appeared here in 1929, became well established by the 1940s, but whose numbers have been sharply reduced several times since then by winters with very heavy snowfall and unusually low temperatures. The latter type of winter can apparently affect established populations of certain insects too, such as the butterfly Orange Sulphur (Colias eurytheme).  

 As noted above, the marine algae population here appears to have shifted its distribution northward more slowly than other groups of organisms, undoubtedly due to the prevailing temperatures and other features of the surrounding ocean. In addition, some groups appear to have invaded up the Atlantic Coastal Plain more quickly than others. As examples, species with primarily southern distributions including several ants and the moth (Lycia ypsilon), of which the female is flightless, arrived before the island was surrounded by water. But three mammal species typical of the adjacent mainland today did not get far enough north to colonize the island before it became one: Woodchuck (Marmota monax), Southern Flying Squirrel (Glaucomys volans), and Eastern Chipmunk (Tamias striatus). The latter species was introduced later; Northern Flying Squirrel (Glaucomys sabrinus) was probably a resident of the pre-colonial forests but was lost during the period of deforestation later (see the Mammal chapter). 

Let us not forget that the invasive species that has had the greatest impact on the biodiversity of Martha’s Vineyard over time has been the human species Homo sapiens. Only time will tell whether this creature will have the wisdom adequately to safeguard the flora and fauna we now have on the island for future residents as well as current ones.

There are several general treatments of Martha’s Vineyard natural history that have been published over the years that may be of interest to readers of this work. Listed chronologically there is a charming description of the annual cycle of life in a fresh-water pond (Mayhew, 1973); a general description of natural history on the island that also includes Cape Cod, Nantucket, Block Island and Long Island (Sterling, 1978); a guide to selected sites on Martha’s Vineyard and the wildlife to be found there (Hale, 1988); an excellent ecological discussion of coastal ponds (Culbert and Raleigh, 2001); a discussion of natural history on Cape Cod covering many topics common to the island (Schwarzman, 2002); and a general guide to nature on Cape Cod and the islands, though a bit weak on Martha’s Vineyard sites (O’Brien, 2003).

Allan Keith; edited by Matt Pelikan, July 18, 2022