It's the same as the plural. EXAMPLE: 1. The species of plant that I like best comes from the same family that roses do. 2. There are many species of fungi that live in this forest.

Julija, just as a side now, there actually is a rare word "specie," but it means something completely different. It is an old-fashioned, rare, legalistic word seen only in old books, or in histories of currency, banking, and money. It meaning money--specifically, cash in the form of coins made of precious metal. When I was a child, in the 1960s, some dollar bills said on them that they were "silver certificates" and that they were worth "one dollar, in silver payable to the bearer on demand." That meant that you could take them to a bank and get four silver quarters for them. At that time, then, silver certificates were "payable in specie on demand." In real life, of course, a bank would also give you four silver quarters in exchange for a one dollar "Federal Reserve note," but one was legally payable in specie on demand, and the other wasn't. Nowadays, there are no "silver certificates," quarters are not made of silver, and no coins have enough value to be practical for serious business transactions. The idea of money being "payable in specie" is out of date, and the word "specie" is, too.

New Oxford American Dictionary species | ˈspisiz, ˈspiʃiz | noun (plural same)

Just for fun, I found few quotations from Darwin's "On the Origin of Species" that illustrate the point that the singular and plural forms are both "species." "a naturalist ... might come to the conclusion that each species [singular] had not been independently created, but had descended, like varieties, from other species [plural]." "...I think it highly probable that our domestic dogs have descended from several wild species [plural]..." "...no other existing species [singular] is thus coloured and marked..." "...After fourteen thousand generations, six new species [plural], marked by the letters n14 to z14, are supposed to have been produced..." "...every naturalist knows vaguely what he means when he speaks of a species [singular]..." A fair number of English words have identical singular and plural forms. One sheep, two sheep; one deer, two deer. Dr. Seuss wrote a book entitled "One Fish, Two Fish, Red Fish, Blue Fish." If the singular form ends in "-s," and a few words do, then the plural will usually be the same. One army corps, two army corps. One crossroads, two crossroads. Things that come in pairs often follow the pattern of "pants." The proper singular form is "a pair of pants." If there are two of them, they are "two pairs of pants." However, with a possessive pronoun, we would just say "my pants," in which case the singular and plural are the same. "I packed my good suit pants" could mean one pair. "I just got all of my suit pants back from the cleaners" could mean several pants. The same pattern applies to "scissors," "pliers," "trousers," "pajamas," etc.