"species complex" meaning in English

{
  "forms": [
    {
      "form": "species complexes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "species complex (plural species complexes)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
            "Entries with incorrect language header",
            "Entry maintenance"
          ],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with 1 entry",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "Pages with entries",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "topical",
          "langcode": "en",
          "name": "Biology",
          "orig": "en:Biology",
          "parents": [
            "Sciences",
            "All topics",
            "Fundamental"
          ],
          "source": "w"
        }
      ],
      "glosses": [
        "A group of closely related species that are very similar in appearance to the point that the boundaries between them are often unclear."
      ],
      "id": "en-species_complex-en-noun-H9gX6uCV",
      "links": [
        [
          "biology",
          "biology"
        ]
      ],
      "raw_glosses": [
        "(biology) A group of closely related species that are very similar in appearance to the point that the boundaries between them are often unclear."
      ],
      "topics": [
        "biology",
        "natural-sciences"
      ],
      "wikipedia": [
        "species complex"
      ]
    }
  ],
  "word": "species complex"
}

{
  "forms": [
    {
      "form": "species complexes",
      "tags": [
        "plural"
      ]
    }
  ],
  "head_templates": [
    {
      "args": {},
      "expansion": "species complex (plural species complexes)",
      "name": "en-noun"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "noun",
  "senses": [
    {
      "categories": [
        "English countable nouns",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English nouns",
        "Pages with 1 entry",
        "Pages with entries",
        "en:Biology"
      ],
      "glosses": [
        "A group of closely related species that are very similar in appearance to the point that the boundaries between them are often unclear."
      ],
      "links": [
        [
          "biology",
          "biology"
        ]
      ],
      "raw_glosses": [
        "(biology) A group of closely related species that are very similar in appearance to the point that the boundaries between them are often unclear."
      ],
      "topics": [
        "biology",
        "natural-sciences"
      ],
      "wikipedia": [
        "species complex"
      ]
    }
  ],
  "word": "species complex"
}